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Straddle monorail steel-concrete composite beam is a new form of railway structure with light weight and convenient installation. The mechanical properties and arrangement of group nail connections are key design parameters to determine the mechanical properties of the straddle monorail steel-concrete composite beam. In order to obtain the mechanical properties of the group nail, this paper carries out experimental research on the group nail of the straddle monorail composite beam, and designs four groups of push-out tests, including three groups of full-scale specimens and one group of 1:3 scale specimens. The research variables include the number of group nails, the arrangement form and size of the specimens. The failure types, load-displacement relationship and main mechanical properties parameters of the specimens are obtained. According to the test results, the failure of the four group of specimens are ductile failure due to bolt shearing, which is consistent with the results of limit deformation analysis. The bolt strains at different locations of the groove of the same specimen are different, presenting a distribution pattern of "large on both sides and small in the middle", which is maintained as the load increases. It can be seen that the group nailing effect reduces the shear bearing capacity of full-scale specimens by about 23.4% to 27.2%, and the more intensive the stud arrangement, the greater the decrease in bearing capacity. Due to the group nailing effect, the shear capacity of the scale specimen is reduced by about 16.5%, which is obviously smaller than that of the full-scale specimen. In general, the mechanical properties of group nail connections are comprehensively studied through tests, and the calculation method of bearing capacity of group nail connections is given by combining existing design specifications and theoretical methods, which provides design suggestions for corresponding engineering applications. [ABSTRACT FROM AUTHOR]

Laminated concrete slabs can deliver desirable structural properties and effectively improve the speed of construction. According to their basic specifications, laminated concrete slabs comprise a 60 mm precast concrete slab and a 70 mm concrete layer cast in situ, with a steel truss bar at a height of 80 mm. This paper studies the effects of the steel truss bar on the mechanical properties of precast slabs. A simple but accurate method is proposed for calculating the stiffness of precast slabs. The test results show that the steel truss bar has a limited effect on the stiffness of the precast slab but will weaken the compression strength of the concrete, resulting in a significant reduction in the ultimate bearing capacity of the precast slab. Further discussions show that eliminating the steel truss bar and appropriately increasing the thickness of the precast slab can effectively increase the stiffness and load-bearing capacity of the precast slab, as well as reduce the consumption of the floor reinforcement by about 26%. [ABSTRACT FROM AUTHOR]

[This corrects the article DOI: 10.1038/s41421-019-0126-6.]., (© The Author(s) 2020.)

Purpose: To compare the anti-gingivitis effect of a power toothbrush relative to a manual toothbrush control., Methods: This was a 3-month, randomized and controlled, single-center, parallel group, examiner-blinded clinical study. 123 Chinese adults in good general health and with at least 15 gingival bleeding sites, as measured by the Gingival Bleeding Index, were enrolled into the study. At baseline, pre-treatment gingivitis levels were assessed using the Mazza Bleeding Index. Subjects were then randomly assigned to receive either an oscillating-rotating power toothbrush [Oral-B Professional Care 7000 (D17u/EB17)] or a flat-trim manual toothbrush with tapered filaments (Lion Dentor Systema). Subjects brushed at home twice-daily with their assigned toothbrush and a marketed sodium fluoride dentifrice (Crest Cavity Protection dentifrice), and were reevaluated at Months 1, 2, and 3., Results: 113 evaluable subjects completed the study. Both groups showed significant reductions in gingivitis from baseline for all time points measured (P< 0.001). At Months 1, 2 and 3, the power toothbrush demonstrated significantly greater gingivitis reductions of 7.11%, 9.20% and 8.47%, respectively, than the manual toothbrush (P< 0.01), and significantly fewer bleeding sites (17.3%, 23.9% and 24.3%, respectively, P< 0.05). No adverse events were reported or observed for either brush during the study., Clinical Significance: The power brush provided statistically significantly greater reductions in gingivitis compared with a manual toothbrush at Months 1, 2 and 3., Competing Interests: Dr. Z. Li and Dr. Zhao declared no conflict of interest. Dr. T. He, Ms. C. Li, Ms. Sun, Ms. Chang, Ms. Y. He, and Mr. Ji are employees of the Procter & Gamble Company. The project was funded by the Procter & Gamble Company.