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Experimental and Numerical Investigation of Stress Concentration at Rib-to-Crossbeam Joint
Heng Fang,Nouman Iqbal,Gilles Van Staen,Hans De Backer 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.1
In orthotropic steel decks (OSDs), the rib-to-crossbeam joint is the most vulnerable detail that has not been drawn enough attention. The failure mode of cracks initiate from the lower weld end on rib wall is governing its fatigue performance. However, relevant detail categories are still missing in prevailing codes. This paper mainly focuses on the stress concentrations at the rib-to-crossbeam joint induced by rib distortions. A series of static load tests were fi rst performed on a full-scale OSD specimen with diff erent weld length between the ribs and the crossbeam. Then, corresponding numerical simulations were fi nished. Several possibilities that may cause the diff erences between the measurements and the calculations are investigated. At last, fatigue assessments based on infl uence lines of structural hot spot stress (SHSS) are completed. Research results reveal that the measurement results of reference points for SHSS method would be very sensitive to the exact location of strain gauges. Due to the manual welding, the deviation of strain gauge positions induced by the irregular weld shape is thought to be the main reason that causes the diff erences between measurements and calculations. Raising the location of cope hole terminations would decrease distortional stresses. However, the infl uence of this parameter on fatigue lives is rather small. The fatigue lives of points along the lower weld toe are very close. Hence, the point at the middle plane of crossbeam could be used as the reference point for fatigue assessments. Meanwhile, the center between ribs could be used as the reference transverse load position for fatigue assessments of this joint.
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Jiang, Shu-Heng,Li, Jun,Dong, Fang-Yuan,Yang, Jian-Yu,Liu, De-Jun,Yang, Xiao-Mei,Wang, Ya-Hui,Yang, Min-Wei,Fu, Xue-Liang,Zhang, Xiao-Xin,Li, Qing,Pang, Xiu-Feng,Huo, Yan-Miao,Li, Jiao,Zhang, Jun-Feng Elsevier 2017 Gastroenterology Vol.153 No.1
<P><B>Background & Aims</B></P> <P>Desmoplasia and poor vascularity cause severe metabolic stress in pancreatic ductal adenocarcinomas (PDACs). Serotonin (5-HT) is a neuromodulator with neurotransmitter and neuroendocrine functions that contributes to tumorigenesis. We investigated the role of 5-HT signaling in the growth of pancreatic tumors.</P> <P><B>Methods</B></P> <P>We measured the levels of proteins that regulate 5-HT synthesis, packaging, and degradation in pancreata from Kras<SUP>G12D/+</SUP>/Trp53<SUP>R172H/+</SUP>/Pdx1-Cre (KPC) mice, which develop pancreatic tumors, as well as in PDAC cell lines and a tissue microarray containing 81 human PDAC samples. We also analyzed expression levels of proteins involved in 5-HT synthesis and degradation by immunohistochemical analysis of a tissue microarray containing 311 PDAC specimens, and associated expression levels with patient survival times. 5-HT level in 14 matched PDAC tumor and non-tumor tissues were analyzed by ELISA. PDAC cell lines were incubated with 5-HT and cell survival and apoptosis were measured. We analyzed expression of the 5-HT receptor HTR2B in PDAC cells and effects of receptor agonists and antagonists, as well as HTR2B knockdown with small hairpin RNAs. We determined the effects of 5-HT stimulation on gene expression profiles of BxPC-3 cells. Regulation of glycolysis by 5-HT signaling via HTR2B was assessed by immunofluorescence and immunoprecipitation analyses, as well as by determination of the extracellular acid ratio, glucose consumption, and lactate production. Primary PDACs, with or without exposure to SB204741 (a selective antagonist of HTR2B), were grown as xenograft tumors in mice, and SB204741 was administered to tumor-bearing KPC mice; tumor growth and metabolism were measured by imaging analyses.</P> <P><B>Results</B></P> <P>In immunohistochemical analysis of a tissue microarray of PDAC specimens, increased levels of TPH1 and decreased level of MAOA, which regulate 5-HT synthesis and degradation, correlated with stage and size of PDACs and shorter patient survival time. We found levels of 5-HT to be increased in human PDAC tissues compared with non-tumor pancreatic tissues, and PDAC cell lines compared with non-transformed pancreatic cells. Incubation of PDAC cell lines with 5-HT increased proliferation and prevented apoptosis. Agonists of HTR2B, but not other 5-HT receptors, promoted proliferation and prevented apoptosis of PDAC cells. Knockdown of HTR2B in PDAC cells, or incubation of cells with HTR2B inhibitors, reduced their growth as xenograft tumors in mice. We observed a correlation between 5-HT and glycolytic flux in PDAC cells; levels of metabolic enzymes involved in glycolysis, the phosphate pentose pathway, and hexosamine biosynthesis pathway increased significantly in PDAC cells following 5-HT stimulation. 5-HT stimulation led to formation of the HTR2B–LYN–p85 complex, which increased PI3K–Akt–mTOR signaling and the Warburg effect by increasing protein levels of MYC and HIF1A. Administration of SB204741 to KPC mice slowed growth and metabolism of established pancreatic tumors and prolonged survival of the mice.</P> <P><B>Conclusions</B></P> <P>Human PDACs have increased levels of 5-HT, and PDAC cells increase expression of its receptor, HTR2B. These increases allow for tumor glycolysis under metabolic stress and promote growth of pancreatic tumors and PDAC xenograft tumors in mice.</P>
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Quan Zhou,Song Yang,Heng Zhang,Fei Chang,Hu Li,Hu Pan,Wei Xue,De-Yu Hu 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.31 No.-
A comparative study on the activity of La2O3 and two kinds of nano La2O3 catalysts prepared usingsonochemical (nano La2O3-S) and hydrothermal methods in the transesterification to produce biodieselwas conducted. The relatively high activity of nano La2O3 catalysts may be ascribed to their high basestrength, large base amount, small particle size and large BET surface areas. Nano La2O3-S was selectedfor further optimisation due to its simple preparation procedure and short preparation time. The FAMEcontent and yield obtained were successively 97.6% and 90.3% under optimal conditions. Moreover, nanoLa2O3-S showed a remarkable tolerance to FFA.
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Effect of pH on the fibroin regulated mineralization of calcium phosphate
Xiao-Dan Sun,Ying-Li Zhou,Juan-Yong Ren,Fu-Zhai Cui,Heng-De Li 한국물리학회 2007 Current Applied Physics Vol.7 No.s1
The eect of pH on the mineralization of calcium phosphate regulated by broin is investigated in this paper. Calcium phosphatesform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results dem-onstrated the great inuence of pH on the formation of calcium phosphate, both in the presence and in the absence of broin. Purehydroxyapatite (Ca10(PO4)6(OH)2,HA) can be obtained at relatively high pH (pH 8.0), while brushite (CaHPO4 Æ2H2O, DCPD) isto HA and regulate the morphology and structure of the HA crystals obtained.
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