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Vehicle collision on reinforced concrete bridge pier (RCBP) frequently occurred all over the world in the past two decades, posing a potential threat to safety of the bridge. However, the impact-resistant design of RCBP in current regulations is only based on the equivalent static force of vehicle impact without considering the damage-performance correlation of the impacted RCBP. This study aims to establish the performance-based design procedure for the typical double-pier RC bridge against vehicle collision. By adopting the refined finite element models of light, medium and heavy trucks with the weight ranging from 3 to 50 t and impact velocity varying from 40 to 120 km/h, 54 numerical simulations of collision scenarios are carried out based on the validated numerical algorithm and material constitutive models. It derives that: (i) the dominated factor that evaluates whether RCBP fails or not under vehicle collision is the peak dynamic shear demand at the base of the RCBP, and related explicit expressions of the peak dynamic shear demand and capacity are further developed and verified; (ii) a new damage index, i.e., the ratio of peak dynamic shear demand to the dynamic shear capacity, is defined to evaluate different damage levels of the RCBP under vehicle collision; (iii) damage-performance correlation of the impacted RCBP is also established, e.g., the bridge is prone to collapse under vehicle collision once damage index exceeds 1.2. Finally, by proposing the impact-resistant performance objectives, the detailed performance-based design procedure is developed according to the importance level of roadway.

Vehicular collision with bridge pier can cause significant structural damage, and even partial or full collapse of the bridge, while the existing work mainly focuses on the vehicular-impact resistance of bridge pier. This study aims to study the collapse process and damage levels of the bridge collided by medium and heavy trucks. Firstly, the refined finite element (FE) model of the typical simply supported two-span double-pier RC bridge is established via the commercial software LS-DYNA, and the adopted material constitutive models and numerical algorithms are validated by comparing with the prototype truck-pier collision test and full-scale drop-weight test on RC beam. Then, the validated FE model is employed to numerically reproduce the actual heavy truck collision accident involving the collapse of bridge, and the dynamic behaviors and collapse process of the collided bridge are analyzed. It shows that, for the present bridge type: (i) truck-bridge collision is not a single impact but a successive impact with bumper, engine and cargo, in which the shear failure on the reinforced concrete bridge pier (RCBP) induced by the engine impact is the dominant factor resulting in the bridge collapse; (ii) during the collision process, the impacted RCBP firstly suffers shear failure at the bottom, and followed by the inclination of the bent cap and superstructure, and then the neighboring RCBP sustains flexible-shear failure at the top, which eventually results in the instability of substructure and collapse of superstructure. Furthermore, a total of 35 truck-bridge collision cases are numerically simulated and assessed, and a new quantitative damage evaluation approach, including the modified damage index, damage level and evaluation criterion, is proposed for the bridge under vehicular collision. In addition, the relationship between the damage level of the collided bridge and superstructure inclination is clarified, which is beneficial for bridge engineers to feasibly assess the vehicular-impact resistance of bridge.

Bridge piers designed according to the seismic specifications are likely to be subjected to the accidental vehicular collisions during its service life cycle, while the correlations between the seismic capacity and impact resistance of bridge pier are rarely studied, as well as the practical damage evaluation approach. This paper aims to fill this research gap. Firstly, four typical double-pier RC bridges are designed based on the Chinese seismic design specifications with consideration of different seismic hazard levels, and the corresponding refined finite element models are established by using LS-DYNA. Then, based on the validated material models and numerical algorithm, the numerical simulations of total 108 vehicle-pier collision scenarios are systemically performed, including the pick-up light truck, Ford 800 medium truck and tractor-trailer heavy truck with different tonnages of 3–30 t and collision velocities of 40–120 km/h. By assessing the pier’s deformation and vehicular impact force, it derives that the bridge pier designed with the enhanced seismic capacity exhibits a lower damage level and survives the higher impact speed of heavy truck, as well as withstands the successive cargo impact. Besides, five potential failure modes of the seismic designed bridge pier under vehicular collisions are identified, i.e., local damage on pier, overall collapse of bridge structure, etc. Finally, a new explicit damage index is proposed by further considering the diameter and shear-span ratio of bridge pier, then the damage levels of the vehicular impacted pier and whole bridge structure are evaluated, and the corresponding damage evaluation diagrams are given. The current work could provide helpful reference in the evaluation and design of RC bridge pier regarding both the earthquake and vehicular collisions.

Vehicle collisions with piers are main threat to bridge structures, thus the impact resistance of pier is significant for bridge structure safety. This paper presents the experimental and numerical work undertaken for investigating the impact process, damage and failure mode, dynamic behavior, and impact resistance evaluation method of reinforced concrete (RC) piers under lateral impact loading. By using a horizontal impact system, a series of simplified truck model collision test on the square sectional RC piers are performed, in which two main designing parameters, i.e., impact velocity and longitudinal reinforcement ratio, are especially concerned. Moreover, the detailed finite element models are established by the commercial program LS-DYNA, which are verified against the test results. It indicates that, the shape of impact force time-history does not exhibit the platform stage compared with that of the conventional drop hammer impact tests attributed to the shear failure mode occurred for the present columns; the damage level, impact force, displacement at impact position and energy dissipation rise with increasing the impact velocity; increasing the longitudinal reinforcement ratio improves the impact resistance of RC piers effectively; a plastic hinge forms with the hoop reinforcement yielding before the shear failure of column; the impact force causes a considerable change of the axial force of RC piers during the impact process. Finally, based on the energy conservation law, the residual displacement at the impact position is adopted and validated as the reasonable criterion for evaluating the impact resistance of RC piers. The present work can provide helpful references for the anti-collision design and impact resistance evaluation of the urban and highway bridge piers.

In early breast cancer patients with sentinel node metastasis, the effect of axillary lymph node dissection (ALND) is controversial. The purpose of this study is to compare the safety and efficacy of sentinel lymph node biopsy (SLNB) alone versus ALND in patients with early breast cancer and sentinel node metastasis.We searched PubMed, Embase, Web of Science, and Cochrane Library databases from 1965 to February 2014. All data were analyzed using Review Manager Software 5.2.12 studies, which included 130,575 patients from five randomized controlled trials and seven observational studies, met our inclusion criteria. 26,870 early breast cancer patients underwent SLNB alone and 103,705 underwent ALND. Patients underwent ALND had more paresthesia (risk ratio [RR] 0.26, 95% confidence interval [CI] 0.20-0.33; p0.01) and lymphedema (RR 0.28, 95% CI 0.20-0.41; p0.01) than those had SLNB alone. There were no significant differences in overall survival (hazard ratio [HR] 0.95, 95% CI 0.85-1.06; p = 0.35), disease-free survival (HR 1.00, 95% CI 0.98-1.02, p = 0.96), and locoregional recurrence (RR 0.92, 95% CI 0.59-1.44; p = 0.73).Current evidence indicates that axillary dissection may be omitted in early breast cancer patients with sentinel lymph metastasis.

Laser quenching (LQ) technique is used as a part of duplex treatments to improve the thickness and hardness of the surface layers of steels. The present study is to investigate the surface properties of low alloy steel treated by plasma nitrocarburizing (PNC) prior to a laser quenching process (PNC+LQ). The microstructure and properties of PNC+LQ layer determined are compared with those obtained by PNC and LQ processes. OM, XRD, SEM and EDS analyses are utilized for microstructure observation, phases identification, morphology observation and chemical composition detection, respectively. Microhardness tester and pin-on-disc tribometer are used to investigate the mechanical properties of the modified layers. Laser quenching of plasma nitrocarburized (PNC+LQ) steel results in much improved thickness and hardness of the modified layer in comparison with the PNC or LQ treated specimens. The mechanism is that the introduction of trace of nitrogen decreases the eutectoid point, that is, the transformation hardened region is enlarged under the same temperature distribution. Moreover, the layer treated by PNC+LQ process exhibits enhanced wear resistance, due to the lubrication effect and optimized impact toughness, which is contributed to the formation of oxide film consisting of low nitrogen compound (FeN0.076) and iron oxidation (mainly of Fe3O4).

By using the first-principles calculations within virtual crystal approximation (VCA) framework, the alloying behavior of transition metals M (M = Cr, Ni, Mo, V, Co, Nb, Mn, Ti and Cu) has been investigated in ternary e-(Fe1−xMx)3N nitrides (x = 0–0.15). The phase stability and elastic properties are studied by calculating the formation Gibbs energy, independent elastic constants and densities of states. The calculated results show that the stability of the e-(Fe1−xMx)3N nitrides decrease with the increase of the substitution content, indicating the decomposition of e phase to α or γ′ phases. The elastic properties of the e-(Fe1−xMx)3N nitrides are sensitive to the transition element types except Co and Mn which show the weakest effect. Densities of states are given for all e-(Fe1−xMx)3N nitrides to confirm the origins of the variations of phase stability and elastic properties. The calculated results show a reasonable agreement with available experimental values.

30CrMnSiA steel has been commonly used in many industrial applications owing to its excellent mechanical properties. However, raw 30CrMnSiA steel cannot meet the requirements of practical application, such as high surface hardness and superior wear resistance. In practice, plasma nitriding (PN) is usually conducted to strengthen the surface properties of this steel. However conventional plasma nitriding (PN) technique is always hindered by diffusion kinetics. Alternatively, the process of laser quenching (LQ) has been utilized as a unique rapid method for tailoring the surface microstructure and chemical composition to improving the mechanical properties of steels. In the present study, a laser quenching technique (LQ) is utilized as subsequent procedure of typical plasma nitriding treatment process (PN) to improve the surface properties of 30CrMnSiA steel. The microstructure and properties of such layer are compared with those obtained by PN or LQ treatment. OM, XRD, SEM and EDS analysis are conducted for microstructure observation, phase identification, and estimating the nitrogen concentration, respectively. Microhardness tester and pin-on-disc tribometer are used to investigate the mechanical properties of the modified layers. Laser quenching of plasma nitrided (PN + LQ) 30CrMnSiA steel results in great increase in the thickness and hardness of the modified layer comparing with the PN and LQ treatment due to the reduction of eutectoid point caused by introduction of nitrogen. The mechanism is also discussed systematically based on the phase diagram in the paper. Moreover, the layer treated by PN + LQ process exhibits better wear resistance than the PN treated specimen. This is attributed to the formation of retained austenite and Fe 3 O 4 according to the XRD analysis, which is beneficial to the improvement of impact toughness and the lubrication action during sliding.

Annealed and quenched M50NiL steel specimens were plasma nitrided at 460°C for 4 h under a mixture gaseous supply of 0·05N2+0·4H2 L min−1 to investigate the effects of the substrate microstructure on the features of nitrided layer, such as microstructure, microhardness and wear resistance. The results show that the nitrided layer is mainly consisted of α′-Fe, γ′-Fe4N and α′N (nitrogen expanded martensite) phases. The surface hardness is significantly enhanced. For the quenched specimens, the nitrided depth decreases with increasing quenched temperature. Compared to the quenched specimens, the nitrided depth of the annealed specimen is thicker under the same nitriding condition. The mechanism may be the variation in the amounts of interstitial carbon atoms and substitution alloying elements in the lattice, and the compressive residual stresses in the substrate. It is also demonstrated that the wear resistance for both the annealed and the quenched specimens can be significantly improved by plasma n...

The microbiome refers to the totality of microorganisms, their collective genetic elements, and environmental interactions, in a specific environment. Trillions of microbes in the mammalian host play important roles in the development of the host immune system and the regulation of host metabolism, affecting myriad aspects of host physiology. Alterations to the normal human microbiome have serious pathological consequences, including the development and progression of many metabolic diseases, such as insulin resistance and diabetes, obesity, inflammatory bowel diseases, cancer, and infection. As a result, the microbiome can be considered as a therapeutic target for pre- and probiotic (or synbiotic) intervention and as a target for drug discovery.

The modern version of epigenetics includes the molecular mechanisms that influence the phenotypic outcome of a gene or genome, in absence of changes to the underlying DNA sequence. A host of genomic interrelationships with the diet evidently exist. The broad topic of nutrigenomics is defined as the interaction between nutrition and an individual's genome. Ruminant species have evolved to metabolize the short-chain volatile fatty acids (VFAs, acetate, propionate, and butyrate) to fulfill up to 70% of their nutrient energy requirements. The potential biological roles of VFAs were investigated using the established Madin-Darby bovine kidney epithelial cell line. Butyrate induces cell cycle arrest and apoptosis in bovine cells. Gene expression profiling indicated that butyrate induces many significant changes in the expression of genes associated with regulatory pathways that are critical to cell growth, immune response and signal transduction. Functional category and pathway analyses of the microarray data revealed that several canonical pathways (the cell cycle G2/M DNA damage checkpoint and G1/S checkpoint regulation; pyrimidine metabolism; and purine metabolism insulin-like growth factor axis components) were significantly affected.