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Now showing items 129 - 144 of 148

  • Synthesis of bioderived polycarbonates with adjustable molecular weights catalyzed by phenolic-derived ionic liquids

    Qian, Wei   Liu, Lei   Zhang, Zengliang   Su, Qian   Zhao, Weizhen   Cheng, Weiguo   Dong, Li   Yang, Zifeng   Bai, Ruibing   Xu, Fei   Zhang, Yanqiang   Zhang, Suojiang  

    The synthesis of high-molecular-weight bioderived polycarbonates via green routes and regulation of molecular weight is of great significance and is highly challenging. Herein, a green sequential approach toward the synthesis of bio-derived polycarbonates with adjustable molecular weights from isosorbide and dimethyl carbonate (DMC) has been developed by employing ionic liquids (ILs) as a class of eco-friendly catalysts. The structures of IL catalysts can be designed readily to control the molecular weight of isosorbide-derived polycarbonates (PIC), which is an attractive advantage of IL catalysts instead of the conventional metal-containing catalysts. In the presence of the [Bmim][4-I-Phen] catalyst, the PIC weight-average molecular weight (M-w) can reach 50 300 g mol(-1). By the combination of the experimental results and DFT calculations, an IL anion-cation synergistic catalytic polymerization mechanism has been proposed, which reveals the nucleophile-electrophile dual activation by H-bonds and charge-charge interactions in catalyzing the formation of PIC. The significance of this study is that it provides guidance for developing IL catalysts for synthesizing higher molecular weight polycarbonates, thereby conveniently leading to a variety of polymers with tunable properties.
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  • Polymeric Ionic Liquid Grafted on Silica for Efficient Conversion of CO2 into Cyclic Carbonates

    Ying, Ting   Su, Qian   Shi, Zijie   Deng, Lili   Cheng, Weiguo   Hua, Wei  

    On the basis of efficient and recyclable criteria for catalytic conversion of CO2 into cyclic carbonates, functionalized polymeric ionic liquids grafted onto the silica (PIL@SiO2) are explored by the polymeric method herein. Among all the prepared PIL@SiO2, the PIL@SiO2 loaded with a high mass fraction (50%) of PIL is the best in catalytic activity, achieving 91% PO conversion, nearly 50% saved than the non-grafted PIL. In addition, the PIL@SiO2 exhibits higher performance than PILs under identical reaction conditions. Subsequent studies concerning recyclability confirm that the as-prepared catalyst is stable after 5 times recycle without obvious loss in activity. This grafting and polymerization process provides an efficient and sustainable way of CO2 conversion in the long term. [GRAPHICS] .
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  • Ionic liquids with multiple active sites supported by SBA-15 for catalyzing conversion of CO2 into cyclic carbonates

    Shi, Zijie   Su, Qian   Ying, Ting   Tan, Xin   Deng, Lili   Dong, Li   Cheng, Weiguo  

    Synthesis of cyclic carbonates via cycloaddition reaction by means of CO2 and epoxides has been thought as an effective method for relieving global warming together with resource shortage. In order to elevate the utilization ratio of ionic liquids and separate catalysts easily after reaction, multi-site ionic liquids were designed and then immobilized on SBA-15 for the conversion of CO2 into cyclic carbonates. By combining the advantages of multiple sites and mesoporous channel, in this work, a certain amount of ionic liquids with multiple active sites were firmly immobilized on modified SBA-15. Among all the immobilized ionic liquids, [IMCA](2)Br-2@SBA-15 presented the best catalytic activity. The result showed high yield (97.4 %) and almost 100 % selectivity of propylene carbonate, which was close to equivalent molar bulk ionic liquids. This superiority could be attributed to the sufficient dispersion of multiple active sites of ionic liquids after being immobilized, enabling efficient use of ionic liquids. Furthermore, the catalyst showed good recyclability after five cycles. By characterization and DFT calculation, the synergistically catalytic mechanism based on multiple sites was proposed.
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  • Hippocampal Protein Kinase C Gamma Signaling Mediates the Impairment of Spatial Learning and Memory in Prenatally Stressed Offspring Rats

    Su, Qian   Zhang, Huiping   Dang, Shaokang   Yao, Dan   Shao, Shuya   Zhu, Zhongliang   Li, Hui  

    Substantial evidence has demonstrated that prenatal stress (PS) impairs spatial learning and memory in offspring. The neuron-specific protein kinase C gamma (PKC gamma) has been proposed to be unique in spatial learning and memory. The present study proposes to determine whether hippocampal PKC gamma is involved in the detrimental effects of PS on spatial learning and memory in offspring, and to further explore the effects of PS-induced PKC gamma-dependent growth-associated protein 43 (GAP-43) and neurogranin (Ng) phosphorylation alteration on calcium/calmodulin-dependent protein kinase II (CaMKII) activation. Prenatal restraint stress models were established, and lentivirus-mediated overexpression of PKC gamma in the hippocampal CA1 area was applied. The results demonstrated that PS impaired spatial learning acquisition and memory retrieval on the MorrisWater Maze test, especially in juvenile female rats. Hippocampal PKC gamma membrane translocation and cytosolic PKC gamma levels were decreased in PS females. The expression of phosphorylated GAP-43 (p-GAP-43) and phosphorylated Ng (p-Ng), as well as phosphorylated CaMKII (p-CaMKII), was significantly reduced in the hippocampus of PS females. Overexpression of PKC gamma in the hippocampal CA1 area recovered the ability of spatial learning and memory in PS female offspring. Furthermore, enhancing PKC gamma reversed PS-induced membrane and cytosolic PKC gamma reduction, and restored levels of GAP-43 and Ng phosphorylation, and CaMKII activation in the hippocampus. In conclusion, PS possibly decreases hippocampal PKC gamma activity, resulting in a reduction of p-GAP-43 and p-Ng, which underlies insufficient CaMKII activation, thereby impairing spatial learning and memory. (C) 2019 IBRO. Published by Elsevier Ltd. All rights reserved.
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  • The Paradox of Dopamine and Angiotensin II-Mediated Na+, K+-ATPase Regulation in Renal Proximal Tubules

    Guo, Fang   Guo, Huicai   Wang, Haiyan   Zhang, Zhe   Liu, Xu   Shi, Xiaolu   Gou, Xiangbo   Su, Qian   Yin, Jian  

    Accumulated studies reported that the natruretic dopamine (DA) and the anti-natruretic angiotensin II (Ang II) represent an important mechanism to regulate renal Na+ and water excretion through intracellular secondary messengers to inhibit or activate renal proximal tubule (PT) Na+,K+-ATPase (NKA). The antagonistic actions were mediated by the phosphorylation of different position of NKA alpha(1)-subunit and different Pals-associated tight junction protein (PATJ) PDZ domains, the different protein kinase C (PKC) isoforms (PKC-beta, PKC-zeta), the common adenylyl cyclase (AC) pathway, and the crosstalk and balance between DA and Ang II to NKA regulation. Besides, Ang II-mediated NKA modulation has bi-phasic effects.
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  • Experimental Study on the Effect of Water on the Properties of Cast In Situ Foamed Concrete

    Zhao, Wenhui   Su, Qian   Wang, Wubin   Niu, Lele   Liu, Ting  

    This study aims to investigate the effect of water on the properties of cast in situ foamed concrete with a dry density of 300-800 kg/m(3) (100 kg/m(3) is a gradient). Firstly, the shrinkage deformation with the curing time and the volumetric moisture content is studied by the drying shrinkage test and improved drying shrinkage test. Secondly, the influence of volumetric moisture content on mechanical properties is assessed. At last, the effects of immersion time and immersion type on the mechanical properties of foamed concrete are studied by considering the water-level conditions. The achieved results show that the shrinkage deformations increase with the curing time for the drying shrinkage test and the improved drying shrinkage test, while the variations are different. The shrinkage deformation increases with the decrease of volumetric moisture content for six dry densities of foamed concrete. Besides, it gradually changes in the early stage, while it changes fast in the later stage. The compressive strength and elastic modulus decrease with the increase of volumetric moisture content for each density. For the water-level unchanged condition, the compressive strength and elastic modulus initially decrease and then slowly increase with the increase of the immersion time. For the water-level changed condition, the compressive strength and elastic modulus of foamed concrete decrease with the increase of immersion time for each dry density, and the rate of early attenuation is high, whereas the rate of later attenuation is limited.
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  • Cascade Claisen and Meinwald Rearrangement for One-Pot Divergent Synthesis of Benzofurans and 2H-Chromenes

    Song, Liyan   Su, Qian   Lin, Xi   Du, Zhihui   Xu, Huiyou   Ouyang, Ming-An   Yao, Hongliang   Tong, Rongbiao  

    A new cascade approach has been developed for the one-pot four-step divergent synthesis of polysubstituted benzofurans and 2H-chromenes, featuring a novel cascade aromatic Claisen rearrangement/Meinwald rearrangement/dehydrative or oxidative cyclization. This new method was demonstrated with 39 examples tolerating different substitutions at an epoxide, allylic ether, and aromatic ring, and we showcased its utility with the first total synthesis of natural product liparacid A in seven steps.
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  • The Self-Sealing Capacity of Environmentally Friendly,Highly Damped,Fibre-Reinforced Concrete

    Huang, Xu   Ge, Jun   Kaewunruen, Sakdirat   Su, Qian  

    Cracks could attenuate the service life of concrete structures because of the intrusion of hazardous substances such as water. In this study, different proportions of Duras S500 fibre were employed to investigate the self-sealing capacity of environmentally friendly, highly damped, fibre-reinforced concrete (EFHDFRC) containing 5% crumb rubber. The workability of EFHDFRC with different proportions of the fibre was investigated by mechanical properties test. The self-sealing capacity was first measured by introducing the ultrasonic pulse velocity (UPV) test combined with the damage degree in a time-dependent manner. In addition, the regained compressive strength test and visual inspection were applied as additional measures of the self-sealing capacity. The experimental results show that EFHDFRC with different proportions of fibre showed the maximum sealing degree between the 42nd and 51st days after casting the concrete. EFHDFRC with 0.1% fibre had the best performance and the maximum self-sealing degree (2.82%). In summary, it has been proven that 0.1% fibre could stimulate the self-sealing capacity of EFHDFRC by bridging cracked concrete. Moreover, it is noted that sufficient space in cracks is essential for precipitation formation, which could seal the cracks. The new insights of this innovative self-healing, high-damping material are essential for industrial applications exposed to dynamic load conditions such as railway turnout bearers and sleepers, highspeed rail track slabs, blast-resistant walls and columns, and so on.
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  • The Relationship Between Thyroid Function and the Prevalence of Type 2 Diabetes Mellitus in Euthyroid Subjects

    Gu, Yeqing   Li, Huihui   Bao, Xue   Zhang, Qing   Liu, Li   Meng, Ge   Wu, Hongmei   Du, Huanmin   Shi, Hongbin   Xia, Yang   Su, Qian   Fang, Liyun   Yu, Fei   Yang, Huijun   Yu, Bin   Sun, Shaomei   Wang, Xing   Zhou, Ming   Jia, Qiyu   Guo, Qi   Chang, Hong   Wang, Guolin   Huang, Guowei   Song, Kun   Niu, Kaijun  

    Purpose: Thyroid hormones (THs) are primarily responsible for the regulation of energy balance and metabolism, suggesting that TH levels may contribute to the development of type 2 diabetes mellitus (T2DM). However, few studies have investigated the relationship between TH and T2DM in a general population. The aim of this study was to evaluate whether serum TH levels within the reference range are related to T2DM. Methods: A cross-sectional study (n =3D 15,296) was performed in Tianjin, China. Serum free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) levels were measured by chemiluminescence immunoassay, and T2DM was defined according to the American Diabetes Association criteria. Multiple logistic regression models were used to assess the sexspecific relationships between FT3, FT4, FT3/FT4 ratios, and TSH quintiles and T2DM. Results: The prevalence of T2DM was 16.2% in males and 7.7% in females. In males, the multivariable-adjusted odds ratios (95% confidence interval) of T2DM for increasing quintiles of FT3, FT4, and FT3/FT4 ratios were 1.00, 0.75(0.63 to 0.89), 0.70(0.58 to 0.84), 0.63(0.52 to 0.76), 0.56 (0.46 to 0.68; P for trend, 0.0001); 1.00, 1.05(0.87 to 1.27), 1.16(0.96 to 1.40), 1.09(0.90 to 1.31), 1.29 (1.07 to 1.56; P for trend =3D 0.01); and 1.00, 0.69(0.58 to 0.83), 0.72(0.60 to 0.86), 0.59(0.48 to 0.71), and 0.55(0.46 to 0.66; P for trend, 0.0001), respectively. Similar results also were observed in females. In contrast, a strong negative correlation between TSHand T2DMwas observed inmales, but not in females. Conclusions: This study demonstrated that decreased FT3, FT3/FT4 ratios, and increased FT4 levels are independently related to a higher prevalence of T2DM in both males and females, and TSH is inversely related to T2DM in males only.
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  • Rotation-Facilitated Rapid Transport of Nanorods in Mucosal Tissues

    Yu, Miaorong   Wang, Jiuling   Yang, Yiwei   Zhu, Chunliu   Su, Qian   Guo, Shiyan   Sun, Jiashu   Gan, Yong   Shi, Xinghua   Gao, Huajian  

    Mucus is a viscoelastic gel layer that typically protects exposed surfaces of the gastrointestinal (GI) tract, lung airways, and other mucosal tissues. Particles targeted to these tissues can be efficiently trapped and removed by mucus, thereby limiting the effectiveness of such drug delivery systems. In this study, we experimentally and theoretically demonstrated that cylindrical nanoparticles. (NPs), such as mesoporous silica nanorods and calcium phosphate nanorods, have superior transport and trafficking capability in mucus compared with spheres of the same chemistry. The higher diffusivity of nanorods leads to deeper mucus penetration and a longer retention time in the GI tract than that of their spherical counterparts. Molecular simulations and stimulated emission of depletion (STED) microscopy revealed that this anomalous phenomenon can be attributed to the rotational dynamics of the NPs facilitated by the mucin fibers and the shear flow. These findings shed new light on the shape design of NP-based drug delivery systems targeted to mucosal and tumor sites that possess a fibrous structure/porous medium.
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  • Synthesis of Nanocrystalline AZ91 Magnesium Alloy Dispersed with 15 vol.% Submicron SiC Particles by Mechanical Milling

    Su, Shitian   Zhou, Jixue   Tang, Shouqiu   Yu, Huan   Su, Qian   Zhang, Suqing  

    The development of a magnesium matrix composite with a high content of dispersions using conventional liquid-phase process is a great challenge, especially for nanometer/submicron particles. In this work, mechanical milling was employed to prepare nanocrystalline AZ91 dispersed with 15 vol.% submicron SiC particles (SiCp/AZ91). AZ91 with no SiCp was applied as a comparative study with the same mechanical milling. In order to investigate the mechanism of dispersing, the morphology evolution of powders and the corresponding SiCp distribution were observed. As the scanning electron microscope (SEM) analysis exhibited, the addition of SiCp accelerated the smashing of AZ91 particles, which promoted the dispersion of SiCp in AZ91. Thus, after mechanical milling, 15 vol.% SiCp, which was smashed from 800 to 255 nm, got uniformly distributed in the Mg matrix. Based on X-ray diffraction (XRD) results, part of the Mg17Al12 precipitate got dissolved, and an Al-supersaturated Mg solid solution was formed. The transmission electron microscopy (TEM) results showed that the ultimate Mg grain (32 nm) of milled SiCp/AZ91 was much smaller than that of milled AZ91 (64 nm), which can be attributed to a pinning effect of submicron SiCp. After mechanical milling, the hardness of SiCp/AZ91 reached 185 HV, which was 185% higher than the original AZ91 and 33% higher than milled AZ91, due to fine Mg grain and submicron dispersions.
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  • Vibration and Long-Term Performance Analysis of Pile-Plank-Supported Low Subgrade of Ballastless Track under Excitation Loads

    Huang, Junjie   Su, Qian   Liu, Ting   Wang, Xun  

    Pile-plank structures are widely applied for high-speed railway built in soft ground in China. It can be used as a reinforcement to improve the behavior of subgrade by providing vertical confinement to increase their stiffness and strength and reduce the subgrade settlement of ballastless track. However, the use of pile-board structure for soft ground reinforcement of high-speed railway is hindered by the existing gap between applications and theories. To verify vibration characteristics and long-term performance of pile-plank-supported low subgrade of ballastless track and the benefit of pile-board structure, an experimental study was conducted on low subgrade of pile-board under excitation loads using both in situ frequency sweeping and cyclic loading experiments. The frequency sweeping experimental results show that the pile-plank-supported low subgrade has smooth stiffness along the longitudinal subgrade and can effectively control the progressive effects of train speed on dynamic stiffness of the subgrade, which ensures driving safety and comfort. The cycle loading experimental results show that the pile-plank-supported low subgrade has favorable long-term dynamic stability, and its dynamic response is uniform along the longitudinal subgrade.
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  • Overexpression of a bifunctional enzyme, CrtS, enhances astaxanthin synthesis through two pathways in Phaffia rhodozyma.

    Chi, Shuang   He, Yanfeng   Ren, Jie   Su, Qian   Liu, Xingchao   Chen, Zhi   Wang, Mingan   Li, Ying   Li, Jilun  

    BACKGROUND: A moderate-temperature, astaxanthin-overproducing mutant strain (termed MK19) of Phaffia rhodozyma was generated in our laboratory. The intracellular astaxanthin content of MK19 was 17-fold higher than that of wild-type. The TLC profile of MK19 showed a band for an unknown carotenoid pigment between those of beta-carotene and astaxanthin. In the present study, we attempted to identify the unknown pigment and to enhance astaxanthin synthesis in MK19 by overexpression of the crtS gene that encodes astaxanthin synthase (CrtS).; RESULTS: A crtS-overexpressing strain was constructed without antibiotic marker. A recombinant plasmid with lower copy numbers was shown to be stable in MK19. In the positive recombinant strain (termed CSR19), maximal astaxanthin yield was 33.5% higher than MK19, and the proportion of astaxanthin as a percentage of total carotenoids was 84%. The unknown carotenoid was identified as 3-hydroxy-3',4'-didehydro-beta,Psi-carotene-4-one (HDCO) by HPLC, mass spectrometry, and NMR spectroscopy. CrtS was found to be a bifunctional enzyme that helped convert HDCO to astaxanthin. Enhancement of crtS transcriptional level increased transcription levels of related genes (crtE, crtYB, crtI) in the astaxanthin synthesis pathway. A scheme of carotenoid biosynthesis in P. rhodozyma involving alternative bicyclic and monocyclic pathways is proposed.; CONCLUSIONS: CrtS overexpression leads to up-regulation of synthesis-related genes and increased astaxanthin production. The transformant CSR19 is a stable, secure strain suitable for feed additive production. The present findings help clarify the regulatory mechanisms that underlie metabolic fluxes in P. rhodozyma carotenoid biosynthesis pathways.=20
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  • PRDX2 in Myocyte Hypertrophy and Survival is Mediated by TLR4 in Acute Infarcted Myocardium

    Jin, Xian   Chen, Chengjun   Li, Dandan   Su, Qian   Hang, Yanwen   Zhang, Peng   Hu, Wei  

    Peroxiredoxin 2 (PRDX2) is an antioxidant and molecular chaperone that can be secreted from tumor cells. But the role of PRDX2 in acute myocardial infarction (AMI) is not clear. In the current study, we demonstrate the role of PRDX2 from clinical trials, H9c2 cells and in a mouse model. ELISA analysis shows that serum concentrations of VEGF and inflammatory factor IL-1 beta, TNF-alpha and IL-6 were increased in AMI patients compared to a control group. The expression of PRDX2 was also upregulated. In vivo experiments show that the expression of PRDX2 inhibits hypoxia-induced oxidative stress injury to H9c2 cells. However, PRDX2 expression promotes TLR4 mediated inflammatory factor expression and VEGF expression under hypoxia conditions. PRDX2 overexpression in H9c2 cells also promotes human endothelial cell migration, vasculogenic mimicry formation and myocardial hypertrophy related protein expression. The overexpression of PRDX2 inhibits ROS level and myocardial injury after AMI but promotes inflammatory responses in vivo. Immunocytochemistry and immunofluorescence analysis show that overexpression of PRDX2 promotes angiogenesis and myocardial hypertrophy. Taken together, our results indicate that PRDX2 plays two roles in acute infarction - the promotion of cell survival and inflammatory myocardial hypertrophy.
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  • Tailoring Molecular Weight of Bioderived Polycarbonates via Bifunctional Ionic Liquids Catalysts under Metal-Free Conditions

    Ma, Congkai   Xu, Fei   Cheng, Weiguo   Tan, Xin   Su, Qian   Zhang, Suojiang  

    Synthesis of bioderived high-molecular-weight polycarbonates over metal-free catalysts is of great importance but also challenging. In this work, a series of 1-butyl-3-methylimidazolium (Bmim) ionic liquids (ILs) were prepared as catalysts for a melt polycondensation reaction of isosorbide and diphenyl carbonate. By modifying the structures of ILs' anions, the number-average molecular weight (M-n) of poly(isosorbide carbonate) (PIC) was effectively tailored. In the presence of a trace amount (0.05 mol % based on isosorbide) of bifunctional [Bmim][CH3CHOHCOO], the synthesized PIC possessed high M-n of 61,700 g/mol and a glass transition temperature of 174 degrees C, both the highest so far to the best of our knowledge. Besides, it was found that the anions with stronger electronegativity and hydrogen bond formation ability were more efficient for the formation of PIC with higher M-n. To modify the flexibility of PIC, poly(aliphatic diol-co-isosorbide carbonate)s with M-n ranging from 34,000 to 75,700 g/mol were also formulated by incorporating with various aliphatic diols. Additionally, based on the experimental results and nuclear magnetic resonance spectroscopy, a possible mechanism of cooperative nucleophilic-electrophilic activation through hydrogen bond formation and electrostatic interactions by the ILs catalyst was proposed.
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  • Carbon dots derived from pea for specifically binding with Cryptococcus neoformans

    Su, Qian   Gan, Lanlan   Liu, Jie   Yang, Xiaoming  

    Herein, we have prepared two kinds of carbon dots (CDs) on the basis of pea (p-CDs) and sesame (s-CDs) through a facile hydrothermal way. Basically, the two CDs described here exhibited obvious superiority mainly including satisfactory stability, non-toxicity and photobleaching resistance, and also the whole synthesis procedures for both p-CDs and s-CDs were environmental-friendly. Significantly, p-CDs showed specific binding with pathogenic fungus of Cryptococcus neoformans, and thereby revealing the potential of staining the fungus. Additionally, we employed Cryptococcus neoformans to infect mice, and utilized p-CDs to trace the positions of the fungus, proving the fluorescent-staining prospect of p-CDs.
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