A genome-wide association study of coat color in Chinese Rex rabbits

Coat color is an important phenotypic characteristic of the domestic rabbit (Oryctolagus cuniculus) and has specific economic importance in the Rex rabbit industry. Coat color varies considerably among different populations of rabbits, and several causal genes for this variation have been thoroughly studied. Nevertheless, the candidate genes affecting coat color variation in Chinese Rex rabbits remained to be investigated. In this study, we collected blood samples from 250 Chinese Rex rabbits with six different coat colors. We performed genome sequencing using a restriction site-associated DNA sequencing approach. A total of 91,546 single nucleotide polymorphisms (SNPs), evenly distributed among 21 autosomes, were identified. Genome-wide association studies (GWAS) were performed using a mixed linear model, in which the individual polygenic effect was fitted as a random effect. We detected a total of 24 significant SNPs that were located within a genomic region on chromosome 4 (OCU4). After re-fitting the most significant SNP (OCU4:13,434,448, p = 1.31e-12) as a covariate, another near-significant SNP (OCU4:11,344,946, p = 7.03e-07) was still present. Hence, we conclude that the 2.1-Mb genomic region located between these two significant SNPs is significantly associated with coat color in Chinese Rex rabbits. The well-studied coat-color-associated agouti signaling protein (ASIP) gene is located within this region. Furthermore, low genetic differentiation was also observed among the six coat color varieties. In conclusion, our results confirmed that ASIP is a putative causal gene affecting coat color variation in Chinese Rex rabbits

Strain rate effect on interfacial bond behaviour between BFRP sheets and steel fibre reinforced concrete

Numerous studies have shown that using steel fibre reinforced concrete (SFRC) and retrofitting with Fibre-reinforced polymer (FRP) composites can improve the strength and ductility of RC structures against impact and explosive loadings. The interface between FRP and concrete has been identified as one of the weakest parts of the FRP strengthened structures subjected to dynamic loading, with debonding failure usually observed as the primary failure mode. In order to properly analysis and design of FRP strengthened reinforced concrete (RC) structures, it is important to understand the dynamic bonding strength between FRP and concrete. An experimental investigation regarding to the dynamic interfacial bond behaviour between basalt fibre (BFRP) sheets and SFRC is carried out in this study. Concrete prisms were made of short steel fibres with three volumetric fractions (i.e. Vf = 0.5%, 1.0%, and 1.5%) to improve the tensile strengths. To achieve different strain rates, the loading velocities varied from 8.33E-6 m/s, 0.1 m/s, 1 m/s, 3 m/s, to 8 m/s. Experimental results show the bond strength and bond-slip were sensitive to strain rate. The loading rate changed the debonding failure modes from concrete substrate failure to interfacial debonding. In addition, the shear resistance of the interface increased with the fibre volume under both quasi-static and dynamic loadings. Based on the testing data, an empirical bond-slip model, incorporating the volumetric fraction of steel fibre and strain rate, is established for FRP-strengthened SFRC structures

Failure behaviors of oriented strand board material under quasi-static and dynamic loads

© 2017 American Society of Civil Engineers. Oriented strand board (OSB) is an engineering material used in the building industry. In lieu of its cost-effectiveness and sustainability, OSB has been used widely as the skin layer of structural insulated panel (SIP), and is usually used in the building as wall panel and roof panel. During its service life, such panels might be subjected to various dynamic loads, such as windborne debris impact. Good understanding of dynamic failure behaviors of OSB material at different strain rates is needed for reliable prediction of the performance of OSB panel under dynamic loading. In this study, quasi-static and dynamic tests were carried out to investigate the static and dynamic failure behaviors of a specific OSB material. The testing results indicated the tensile strength of OSB was sensitive to strain rate. The damage mode under quasi-static loading condition was found to be different from that under dynamic loading condition, which affected the tensile strength of OSB material. An empirical formula was derived to predict the tensile strength enhancement of OSB material under different strain rates based on the testing results

Inertial Effect on RC Beam Subjected to Impact Loads

© 2017 World Scientific Publishing Company.A simply supported reinforced concrete (RC) beam only experiences sagging moment under static loads while it might experience both sagging and hogging moments under impact loads due to the inertial effect. In order to investigate inertial effect on the impact behavior of RC beam, a numerical model is developed by using the finite element code LS-DYNA. The strain rate effect of the material is considered in the numerical model. The numerical model is calibrated with the testing results of drop weight impact on RC beams available in the literature. The numerical results show that the prediction is better than some other researchers' predictions in terms of peak impact force and peak deformation. In addition, inertial effect is quantitatively evaluated by the peak impact force and the peak hogging moment. The relationship between the peak hogging moment and the peak impact force of the beam is investigated by conducting parametric studies with regard to various net spans, impact masses and impact velocities. The empirical formulae are then proposed to predict the peak impact force and the peak hogging moment. The predications by the proposed empirical formulae are compared with the testing results and the predicted results by other formulae available in the literatures