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The safety of shear design method in the 'code for design of concrete structures' ( GB 50010-2010) for reinforced concrete members without web reinforcement was examined based on the analysis of the thick slab in a bridge that failed in shear. Based on the results of shear tests conducted on large beams with depths ranging from 500 mm to 1 200 mm, and test data of large beams and thick slabs from other researchers, the code expressions for shear strength of members without web reinforcement were evaluated. The influence of minimum web reinforcement and distributed longitudinal reinforcement on shear strength of large members was also discussed. It is shown that the shear strength of large members without web reinforcement exhibits significant size effect such that the code expressions into which a size effect factor has been incorporated are unable to characterize the influence of depth on shear strength of members, resulting in unsafe results when applying to deep beams (a/h0 < 2. 0) with low longitudinal reinforcement ratio and with depth greater than 1 000 mm, and to slender beams (a/h0 ⩾2. 0) with longitudinal reinforcement less than 1. 00% or with depth greater than 1 000 mm. Minimum stirrups required by code provisions are found to be effective for large members to avoid brittle shear failure, while distributed longitudinal reinforcement is less effective for member with depth over 1 000 mm without web reinforcement. [ABSTRACT FROM AUTHOR]

Six reinforced high-strength concrete beam-type specimens of different sizes with stubs columns in the middle were fabricated, and tested under low-cycle reversed loading to investigate the effect of depths on flexural behavior of reinforced high-strength concrete beams. The parameters of specimens varied in depths and ratios of longitudinal reinforcement on the top of cross sections, while the depth-width ratios of cross sections, shear span-to-depth ratios and ratios of longitudinal reinforcement on the bottom of cross sections and stirrups were constant. C70 concrete was used to cast the specimens and HRB 400 steel bars were used as longitudinal reinforcement. The influence of beam depths on nominal cracking moment, nominal yield moment, nominal ultimate moment, displacement ductility, plastic rotation capacity, stiffness degradation and energy dissipation capacity of high-strength concrete beams were investigated. It is shown that there is no apparent size effect observed on nominal cracking moment, nominal yield moment and nominal ultimate moment of reinforced high-strength concrete beams, and that all specimens subjected to cyclic loading clearly show similar stiffness degradation which is independent of beam depths, while the displacement ductility factors, rotational capacity as well as work index of specimens decrease with increasing of depths, showing significant size effect. [ABSTRACT FROM AUTHOR]

Concrete specimens with different sizes confined by stirrups were tested under axial compression. Prisms with aspect ratio of 3:1 were used in the test. The specimens were divided into four groups and each group contained three identical specimens. The sectional dimensions of specimens of the four groups were 108 mm, 200 mm, 250 mm and 370 mm, respectively. To ensure identical confinement coefficient for specimens with different sizes, the same type of confining stirrups were adopted in all specimens and both diameters and spacing of confining stirrups were properly scaled. The influence of specimen size on axial compressive strength and its corresponding peak strain and ductility of confined concrete were investigated. Similar cracking patterns and failure modes were found in the test regardless of sizes of the specimens and steeper descending branches in load-axial strain curves were observed in specimens with larger sizes. It is found that there is not apparent size effect phenomenon with respect to axial compressive strength of confined concrete, while peak strains of confined concrete corresponding to the peak stresses decrease significantly with the increase of specimen sizes. The average peak strain of specimens of 370 mm is 49% of that of specimens of 108 mm showing a significant size effect. [ABSTRACT FROM AUTHOR]

Reinforced high-strength concrete beams subjected to bending were tested to investigate the effect of depth on flexural behavior of beams. The geometry of specimens varied in cross sections with the depth-width ratios of the cross sections, the shear span ratios and longitudinal reinforcement ratios of specimens being constant. C70 concrete was used to cast the specimens and HRB 400 steel bars were used for the longitudinal reinforcement. The influence of beam depth on the nominal cracking moment, nominal yield moment, nominal ultimate flexural moment, ductility, and plastic rotation capacity of high-strength concrete beams was investigated. It is shown that there is no apparent size effect on nominal cracking moment, nominal yield moment and nominal ultimate moment of reinforced high-strength concrete beams. But the displacement ductility ratio and plastic rotation capacity show significant size effect. The displacement ductility factor and the rotational capacity of high-strength concrete beam decrease with the increasing of cross section. [ABSTRACT FROM AUTHOR]

The problem of the inverse of block period tridiagonal matrices are discussed. Using the recursion method , the inversion of higher-order block period tridiagonal matrices are changed into the inversion of low-order block tridiagonal matrices, then a new algorithm for inverse of a block period tridiagonal matrix is given. Compared with the normal algorithm, the new algorithm is shorter in computation. The new algorithm has the computational complexity of 4n2 + 0 ( n), while the algorithm of the direct inversion has the computational complexity of 5. 5n2 + 0( n). The numerical examples show that the calculation time of the new algorithm is shorter and the precision is higher. [ABSTRACT FROM AUTHOR]

Based on modified compression field theory and bending theory of steel fiber reinforced concrete (SFRC) beams, a sectional analysis approach for predicting shear strength of SFRC beams with local stress check at cracks is presented. A tensile stress-strain curve considering tension-stiffening effect is suggested based on the comparative study of the predicted shear strength obtained by three tensile stress-strain curves of SFRC with experimental results. Moreover, the effect of local stress check at cracks on the predicted shear strength is discussed. 44 fiber reinforced concrete beams with shear-to-span ratios more than 2. 0 subjected to shear are analyzed and a good correlation between predicted shear strength and experimental results is achieved. [ABSTRACT FROM AUTHOR]

We investigated the contribution of locomotor activity and learning and memory abilities to Alzheimer's disease induced by metal neurotoxicity. The metal neurotoxicity model was established by using locomotor activity tests and activity-avoidance conditioning paradigms, and observing changes in zebrafish behaviors after exposure to 50 μg/L of AlCl(3) with different pH values (pH 7.8, pH 6.8 and pH 5.8) for 24 hours and 96 hours. The results showed Alzheimer's disease-like behavior in locomotor activity tests and activity-avoidance conditioning paradigms by zebrafish receiving AlCl(3) in pH 5.8 significantly decreased compared to the control group and groups receiving AlCl(3) in pH 7.8 and pH 6.8 for 96 hours and 24 hours. These results provide evidences that exposure to AlCl( 3) in an acid environment can influence locomotor activity and learning and memory abilities in zebrafish. In addition, exposure time and concentration of Al induced neurotoxicity and damaged the brain area of memory, resulting in Alzheimer's disease-like behavior.

Aim: To investigate the effect of morphine on fetal movement, heart rate, hatch weight, hatch days and hatch rate., Methods: Morphine was injected into airspace of eggs and fetal movement, heart rate, hatch weight, hatch days and hatch rates were recorded., Results: Hatch days were shorter, hatch rates were lower and some chicks became motor disorder for morphine. Chicks with morphine exposure 20 mg/kg from E 12 to E 16 had highest hatch rate and lowest disable rate. Morphine reduced fetal movement, increased heart rate (P < 0.05)., Conclusion: The development of chick embryo is impaired by morphine exposure and the magnitude of these effects depends on the drug dose and the length of time that the developing organism is exposed to morphine.

Objective: To investigate the effect of curcumin on the proliferation, cell cycle distribution and apoptosis of hepatocarcinoma cell line QGY., Methods: The MTT method was used to assay the biologic activities of curcumin in different times and different doses. The cell cycle distribution was detected by flow cytometic analysis. The cell ultrastructure was observed by electronic microscopy., Results: Curcumin could inhibit effectively QGY in a dose- and time- dependent manner. IC(50) of curcumin to QGY was 49.50 micromol/L in 72 hours. The cell growth was arrested at S stage. Curcumin could lead to the degeneration, necrosis, and apoptosis., Conclusions: Curcumin can interrupt the cell cycle and has a role in cytotoxicity, antiproliferation and inducing apoptosis of QGY.