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The connecting part of bridge widening undertakes complicated forces and tends to crack. Basic magnesium sulfate cement concrete has excellent properties such as ideal early strength and tensile strength, meeting the performance requirements of joint materials. Experiments of two spliced box girder specimens with C40 basic magnesium sulfate cement concrete (MC) and normal Portland cement concrete (NC) as joint materials are carried out. Concrete strain, reinforcement strain, deflection and crack propagation law of the joint section are tested and analyzed under symmetrical loading at the cantilever of the box girders. The study shows when MC material is used in the splicing section, the joint section showed a multi-cracks failure mode with an ultimate load ratio of 0.99 and a maximum crack width of 1.3 mm; NC joint section has only three longitudinal cracks with an ultimate load ratio of 0.97 and a maximum crack width of 0.98 mm. Under the same load, the crack width and the deflection of mid-span MC joint section are greater than which of NC joint section. The maximum deflection of NC splicing section is 1.20 mm, which is 1/633 of the calculating span length. The maximum deflection of MC spliced section is 2.03 mm, which is 1/374 of the calculating span length. Comparison of the maximum deflection and the maximum crack width shows that MC material has better ductility. [ABSTRACT FROM AUTHOR]

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Through the flexural behavior test of coral aggregate reinforced concrete beams (CARCB) and ordinary Portland reinforced concrete beams (OPRCB), and based on the parameters of concrete types, concrete strength grades and reinforcement ratios, the crack development, failure mode, midspan deflection and flexural capacity were studied, the relationships of bending moment-midspan deflection, load-longitudinal tensile reinforcement strain, load-maximum crack width were established, and a calculation model for the flexural capacity of CARCB was suggested. The results showed that with the increase in the reinforcement ratio and concrete strength grade, the crack bending moment (Mcr) and ultimate bending moment (Mu) of CARCB gradually increased. The characteristics of CARCB and OPRCB are basically the same. Furthermore, through increasing the concrete strength grade and reinforcement ratio, Mcr/Mu could be increased to delay the cracking of CARCB. As the load increased, crack width (w) would also increase. At the beginning of the loading, w increased slowly. And then it increased rapidly when the load reached to the ultimate load, which then led to beam failure. Meanwhile, with a comprehensive consideration of the effects of steel corrosion on the loss of steel section and the decrease of steel yield strength, a more reasonable calculation model for the flexural capacity of CARCB was proposed. [ABSTRACT FROM AUTHOR]

Drug-resistance epilepsy (DRE) is attributed to the brain P-glycoprotein (P-gp) overexpression. We previously reported that nuclear factor-kappa B (NF-κB) played a critical role in regulating P-gp expression at the brain of the acute seizure rats. This study was extended further to investigate the interaction effect of NF-κB and pregnane X receptor (PXR) on P-gp expression at the brain of chronic epileptic rats treated with carbamazepine (CBZ). The chronic epileptic models were induced by the micro-injection of kainic acid (KA) into rats' hippocampus. Subsequently, the successful models were treated with different intervention agents of CBZ; PMA(a non-specific PXR activity inhibitor) or PDTC(a specific NF-κB activity inhibitor) respectively. The expression levels of P-gp and its encoded gene mdr1a/ b were significantly up-regulated on the brain of KA-induced chronic epilepsy rats or the epilepsy rats treated with CBZ for 1 week, meanwhile with a high expression of PXR. The treatment of PMA dramatically reduced both PXR and P-gp expressions at the protein and mRNA levels in the chronic epilepsy brain. By compared to the epilepsy model group, the P-gp expression was not markedly attenuated by the inhibition of NF-κB activity with PDTC treatment, nevertheless with a decrease of NF-κB expression in this intervention group. Higher levels of proinflammatory cytokines(IL-1β, IL-6, TNF-α) were found both in the brain tissue and the serum in the epilepsy rats of each group. There was a declined trend of the pro-inflammatory cytokines expression of the PDTC treatment group but with no statistical significance. This study demonstrates for the first time that P-gp up-regulation is due to increase PXR expression in the chronic phase of epilepsy, differently from that NF-κB signaling may induce the P-gp expression in the acute seizure phase. Our results offer insights into the mechanism underlying the development of DRE using or not using CBZ treatment. [ABSTRACT FROM AUTHOR]

Triploid Chinese loach, Misgurnus anguillicaudatus, hybrids between tetraploids from Hubei Province and diploids from Liaoning Province were mated with either diploid wild-type or triploid hybrids to analyze viability and ploidy of the resultant progenies. Both triploid males and females generated fertile gametes, but progenies from the crosses using gametes of triploid hybrids did not survive beyond the larval stages. In crosses between wild-type diploid females and triploid hybrid males, embryos ranging from 2.2n to 2.6n were predominant with a mode of either 2.4n (chromosome numbers 59, 60, 61) or 2.5n (chromosome numbers 62, 63). Those from the crosses between triploid hybrid females and diploid males gave a modal ploidy level at approximately 2.5n in one case, but a shift to a higher ploidy level was observed in other embryos. In the progenies between triploid hybrid females and males, the ploidy level at approximately 3.0n (chromosome numbers 74, 75, 76) was most frequent. The cytogenetic results of the progenies suggest the production of aneuploid gametes with a modal ploidy level at approximately 1.5n in triploid hybrids. However, a shift to higher chromosome numbers in gametes was observed in certain cases, suggesting the involvement of mortality selection of gametes and/or zygotes with lower chromosome numbers. [ABSTRACT FROM AUTHOR]

Here, we showed meiotic chromosome configurations prepared from oocyte germinal vesicles and spermatocytes of triploid loaches produced from reciprocal crosses between wild-type diploids (2n = 50) obtained from Dalian, Liaoning Province, China and natural tetraploids (4n = 100) from Chibi, Hubei Province, China. Major meiotic cells in triploids comprised 25 bivalents and 25 univalents, but cells with one to five trivalents were also observed. When three homologous chromosomes bearing nucleolar organizing regions (NOR) were identified with the detection of signals or positive sites by silver staining, chromomycin A staining and fluorescence in situ hybridization with a 5.8S + 28S rDNA probe, two third of selected triploid cells gave a configuration including one bivalent with two NORs (association of two homologous chromosomes) and one univalent with one NOR. However, other triploid cells showed three univalent each of which had one NOR, suggesting a failure of synapsis between homologous chromosomes. These results suggested that triploid female and male should produce aneuploid gametes with the theoretical mode at 1.5n (37 or 38 chromosomes). [ABSTRACT FROM AUTHOR]