Search

Ubiquitination-dependent histone crosstalk plays critical roles in chromatin-associated processes and is highly associated with human diseases. Mechanism studies of the crosstalk have been of the central focus. Here our study on the crosstalk between H2BK34ub and Dot1L-catalyzed H3K79me suggests a novel mechanism of ubiquitination-induced nucleosome distortion to stimulate the activity of an enzyme. We determined the cryo-electron microscopy structures of Dot1L-H2BK34ub nucleosome complex and the H2BK34ub nucleosome alone. The structures reveal that H2BK34ub induces an almost identical orientation and binding pattern of Dot1L on nucleosome as H2BK120ub, which positions Dot1L for the productive conformation through direct ubiquitin-enzyme contacts. However, H2BK34-anchored ubiquitin does not directly interact with Dot1L as occurs in the case of H2BK120ub, but rather induces DNA and histone distortion around the modified site. Our findings establish the structural framework for understanding the H2BK34ub-H3K79me trans-crosstalk and highlight the diversity of mechanisms for histone ubiquitination to activate chromatin-modifying enzymes.

The chemical synthesis of homogeneously modified histones is a powerful approach to quantitatively decipher how post-translational modifications (PTMs) modulate epigenetic events. Herein, we describe the expedient syntheses of a selection of phosphorylated and ubiquitinated H2AX proteins in a strategy integrating expressed protein hydrazinolysis and auxiliary-mediated protein ligation. These modified H2AX proteins were then used to discover that although H2AXS139 phosphorylation can enhance the binding of the DNA damage repair factor 53BP1 to either an unmodified nucleosome or that bearing a single H2AXK15ub or H4K20me2 modification, it augments 53BP1's binding only weakly to nucleosomes bearing both H2AXK15ub and H4K20me2. To better understand why such a trivalent additive effect is lacking, we solved the cryo-EM structure (3.38 Å) of the complex of 53BP1 with the H2AXK15ub/S139ph_H4K20me2 nucleosome, which showed that H2AXS139 phosphorylation distorts the interaction interface between ubiquitin and 53BP1's UDR motif. Our study revealed that there is redundancy in the interplay of multiple histone PTMs, which may be useful for controlling the dynamic distribution of effector proteins onto nucleosomes bearing different histone variants and PTMs in a time-dependent fashion, through specific cellular biochemical events.

Ceramic aggregate has the characteristics of light weight, heat insulation, and low cost, and recycled aggregate is a type of green material that realizes the re-crushing of construction waste. This paper studied the impact of replacing natural coarse aggregate with ceramic aggregate and natural sand with recycled fine aggregate, on the physical, mechanical, and thermal properties of concrete. Recycled fine aggregate was used to completely replace natural sand. A total of five concrete mixes (including a reference mix) were prepared with different levels of ceramic aggregate (0%, 30%, 50%, 70%, 100%). Density, compressive strength, thermal conductivity, and thermal inertia index were measured to evaluate the performance of each mixture, and ceramic concrete board and hollow blocks were designed for testing the thermal properties. Results of testing show that density, strength, and thermal performance are interrelated. The smaller the density, the lower the strength, and it indicates that ceramic aggregate has a negative influence on strength in concrete. Meanwhile, the smaller the density, the higher the thermal resistance, and the addition of ceramic aggregate can improve the thermal insulation of concrete. The mechanical and thermal properties are both affected by the ceramic replacement ratio. Ceramic aggregate improves the thermal properties of recycled concrete, and the negative influence of ceramic aggregate on compressive strength can be controlled by the replacement ratio of aggregate in concrete. Based on the overall comparison and analysis, a mix with 50% ceramic aggregate shows relatively better strength and thermal insulation compared to other mixes. The use of ceramic aggregate in combination with recycled fine aggregate can effectively reduce the environmental pollution and make an economical substitute for their natural counterparts.

The structural performance of a frame joint is particularly important, which can determine the safe state of the global structure. For this reason, the seismic performance of the truss steel reinforced concrete (SRC) beam-column frame joints is investigated by the experimental study and the nonlinear finite element modeling. The main design parameters include the section size of the web rods, the axial compression ratio and the section size of I-steel. The failure mechanism, load-displacement skeleton curve, the ductility and energy dissipation capacity, and shear deformation in the core zone of the truss SRC beam-column joints are studied. A formula is put forward to describe the shear bearing-capacity of the joints. The results indicate that the truss SRC beam-column frame joints generally have good seismic performance. The size of steel and web members have impact on the seismic performance of the truss SRC beam-column joints, and the axial compression ratio is an important factor that impacts the hysteresis behavior and energy dissipation. The proposed shear bearing-capacity formula can objectively reflect the performance of the joints.

The mechanical properties of recycled aggregate concrete under multiaxial compression were tested by servo-controlled setup (TAWZ-5000/3000). Properties of strength and stress–strain relation were obtained, and the influence factors of stress ratio and recycled coarse aggregate replacement ratio were analyzed. The results show that the strength of recycled aggregate concrete under multiaxial compression is higher than that of under uniaxial state, the stress ratio and recycled coarse aggregate replacement ratio have obvious effect on strength, and the shape of stress–strain curve is also varied with different levels of the two factors. Failure criterion can reflect the strength relation for recycled concrete under multiaxial stress state. Kupfer’s failure criterion is selected to describe strength properties under biaxial stress state, and the failure envelope reflects the energy absorption of different mix series. Based on octahedral stress theory, the tensile and compressive meridians have been proposed to analyze the strength characteristics under triaxial compression, and the theoretical values are well coherent with the test data.

Coral materials have been used as concrete aggregate for decades to achieve self-sufficiency of materials and reduce costs of island construction. Considering the aggressive environment of islands, filling concrete into steel tube to produce coral concrete-filled steel tube (CCFST) columns is impractical. The combination of concrete and aluminium tube is proposed to avoid steel corrosion and optimize concrete performance in island construction. This study experimentally investigated the axial compression performance of nine coral concrete-filled aluminium tube (CCFAT) square stub columns. The failure mode, load-carrying capacity, and load-deformation relations were obtained, and the effects of concrete strength (fc), aluminium ratio (α), and confinement factor (ξ) on the strength, stiffness, and ductility performance were discussed. Moreover, the adaptability of concrete-filled steel tube (CFST) design codes in the load-carrying capacity prediction of CCFAT square stub columns was assessed. The results show that the increase in α mostly improves the strength index (SI) and stiffness index (KI) while the effects of fc is less significant. The ductility index (DI) and composite action are closely correlated to ξ. Using the design equation in AIJ code to predict the load-carrying capacity of CCFAT square stub columns is acceptable.

To investigate the effect of classification of recycled coarse aggregate on the mechanical behaviors of recycled aggregate concrete (RAC), a total of 150 RAC testing blocks were designed based on the Chinese standard GB/T 25177-2010, taking recycled coarse aggregate and substitution ratio as factors in a series of tests, including cubic compression, prismatic compression, quadrate plate compression and elastic modulus. During the whole testing period, from initial compression to destruction, important characteristic parameters such as stress–strain curve, elastic modulus, peak stress, and peak strain were obtained. The effect of classification of recycled coarse aggregate on the destruction mechanism and mechanical performances of RAC is investigated and analyzed based on the test phenomenon, microscopic structure evolution, damage process,displacement ductility, energy dissipation ability, constitutive relationship, etc. It is understood from the test results that cubic compressive strength, prismatic compressive strength, elastic modulus and damage development speed all follow a tendency of Class I > Class II > Class III, while deformation ductility coefficient has a tendency of Class II > Class I > Class III. Moreover, damage constitutive relationship of RAC is brought forward showing that the theoretical approach can fully reflect the experimental results.

This paper studied the shear behavior of three types of recycled aggregate concrete with different replacement levels of recycled coarse aggregate. Sixty cube specimens and thirty beam specimens with uniform depth and varying width were designed to test their mechanical parameters including cube compressive strength, splitting tensile strength, shear strength, peak shear strain, shear stress-strain curves, and shear modulus. We analyzed how these parameters are influenced by the type of recycled coarse aggregate and by recycled coarse aggregate replacement level. We established the strength conversion equations, one-parameter polynomial non-dimensional shear stress-strain equations, and shear modulus calculation formulas of three types of recycled aggregate concrete. It is found that the strength of recycled aggregate concrete I isslightly lower than that of conventional concrete and decrease with the increase of recycled coarse aggregate replacement level. However, the strength of recycled aggregate concrete II and recycled aggregate concrete III is slightly higher than that of conventional concrete when the recycled coarse aggregate replacement ratio is less than 70%. As the recycled coarse aggregate replacement ratio increase, the peak shear strain of three types of recycled aggregate concrete gradually decreases. The shear strength and peak scant shear modulus of three types of recycled aggregate concrete show the rule of recycled aggregate concrete III > recycled aggregate concrete II > recycled aggregate concrete I. Furthermore, the calculated values of several equations established by the authors agree well with the test values.

The mechanical properties of recycled concrete under biaxial compression were tested in this study. Five grades of replacement ratio of recycled coarse aggregate (0%, 30%, 50%, 70%, 100%) and four groups of stress ratio (−0.25:−1, −0.5:−1, −0.75:−1, −1:−1) were designed to evaluate their influence on mechanical properties.The strength and deformation values of concrete specimens were tested by servo-controlled static-dynamic triaxial machine (TAWZ-5000/3000). The result shows that the stress and strain of recycled concrete under biaxial compression were both higher than the corresponding values that under uniaxial compression. The stress ratio and recycled aggregate ratio have different effects on mechanical properties of concrete. The initial elastic modulus was also affected by the two factors. Based on the analysis of the test data and combined with the stress-strain curve, a constitutive model for recycled concrete under biaxial compressive state was proposed. The comparison between the test results and the fitted curves shows that the proposed model can suitably describe the stress-strain relationship for recycled concrete.

In this paper, X ray diffraction test and Scanning electron microscope test were designed to investigate the effect of limestone powder (LP) in manufactured sand on the hydration products and microstructure of full recycled coarse aggregate concrete samples. The results showed that most of LP was inactive, except only a small quantity of LP participated in the hydrating reaction at mid-late period. This small amount of LP did not change the composition of hydration products but varied their morphology. Some amount of LP filled in the pore structure of cement matrix and in the interface between recycled coarse aggregate and new harden cement paste, improving the compactness of the cement matrix and the interfacial transition zone. The nucleation around the LP who filled in the pore structures was also observed, and the hydration products gradually formed and subsided on the surface of these LP and accelerated the cement hydration.

This paper investigates the bond behavior of deformed bars embedded in recycled aggregate concrete (RAC) subjected to uniaxial lateral pressure. Sixty pull-out specimens with different levels of recycled coarse aggregate (RA; i.e. 0%, 30%, 50%, 70% and 100%) were manufactured, and then these specimens were submitted to test the bond-slip curves under different levels of uniaxial lateral pressure (i. e. 0, 0.1fcu, 0.2fcu, and 0.3fcu). The effects of lateral pressure and RA content on bond strength, peak slip, residual bond strength and bond energy density were analyzed; the bond-slip relationship between RAC and deformed bars was also established. The results demonstrated that the bond strength of reinforced RAC is comparable with that of reinforced natural aggregate concrete (NAC). It is feasible to adopt RA in structural application but the bond ductility should be improved before it can be reliable reused. With the incremental of lateral pressure, the peak slip, relative bond strength and the bond energy density gradually increased, while the relationship between these parameters and RA content could not be clearly observed. In addition, the parameter value for descending bond-slip curve was abruptly decreased after lateral pressure was applied, demonstrating that the lateral pressure increased the bond ductility of RAC specimens.

Linear (Met1-linked) ubiquitination is involved inflammatory and innate immune signaling. Previous studies have characterized enzymes regulating the addition and removal of this modification in mammalian systems. However, only a few plant-derived deubiquitinases targeting Met1-linked ubiquitin chains have been reported and their mechanism of action remains elusive. Here, using a dehydroalanine-bearing Met1-diubiquitin suicide probe, we discover OTUB1 from Oryza sativa (OsOTUB1) as a Met1-linked ubiquitin chain-targeting deubiquitinase. By solving crystal structures of apo OsOTUB1 and an OsOTUB1/Met1-diubiquitin complex, we find that Met1 activity is conferred by Met1-specific motifs in the S1’ pocket of OsOTUB1. Large-scale sequence alignments and hydrolysis experiments provide evidence that these motifs are a general determinant of Met1 activity in the OTUB subfamily across species. Analysis of the species distribution of OTUBs capable of hydrolysing Met1-linked ubiquitin chains shows that this activity is conserved in green plants (Viridiplantae) and does not exist in metazoans, providing insights into the evolutionary differentiation between primitive plants and animals.

In recent years, the mechanical behavior of recycled aggregate concrete (RAC) under different condition has attracted great attention from researchers. As RAC can make full use of the concr...

To evaluate the ductility and energy dissipation capacity of the beam with concrete-encased steel truss, eight specimens with different types of steel truss, reinforcement ratios, and shear span ratios were tested by low-cyclic loading regime. The results indicated that beams with concrete-encased steel truss performed plumped load–displacement hysteretic loops as well as high strength and stiffness. Moreover, cross-web members improved their seismic behavior more effectively than non-cross-web members. Finally, the restoring force model of concrete-encased steel truss beam is proposed in accordance with the experimental results, which can be used to predict the load–displacement behavior of concrete-encased steel truss beam. The results could also provide a reference for the design and application of concrete-encased steel truss beam in practice.

The steel-truss-reinforced composite beam is a type of steel-reinforced concrete structure, in which the concrete beam is reinforced by steel trusses. Unlike traditional reinforced concrete structures, the steel truss works as the main skeleton and takes the main responsibility for the whole structural strength. In order to fulfil energy dissipation requirements, diagonal angle steel crosses are placed at the end of the steel truss. Specimens are designed based on different key parameters, including axial compression ratio and dimensions of chord, web and angle steels. Low-cyclic reversed loading tests are carried out on eight interior joint specimens to simulate realistic reversed loading conditions under earthquake. Load–deflection hysteresis loops and skeleton curves of joint specimens are obtained. Ductility, hysteresis behaviour and seismic-resistant performance are evaluated. Equivalent viscous-damping coefficients and energy dissipation indicators are calculated. The influences of axial compression ratio and steel ratio on the seismic performances are analysed. It is found that a large steel ratio will generally increase the bearing capacity. However, a relatively high axial compression ratio will benefit the bearing capacity of joints, but has adverse effects on hysteresis behaviours. Further, some conclusions are drawn on the overall seismic performances of this type of joint.

Experiment was carried out to better understand the behaviors of recycled aggregate concrete under triaxial compressive stresses. The test was performed on 100 mm × 100 mm × 100 mm cubic specimens with five replacement ratios of recycled coarse aggregate (RCA) at four kinds of stress ratios, using a servo-controlled static-dynamic triaxial machine (TAWZ-5000/3000). The failure modes, ultimate strength and deformation under triaxial compression were observed, and the effect of RCA replacement ratio and stress ratio on these characteristics was analyzed. The results show that the triaxial compressive strength of the specimens is much higher than the corresponding uniaxial strength, and the strength and deformation depend on both RCA replacement ratio and stress ratio. Moreover, the factors affecting triaxial strength were quantitatively analyzed by variance calculation. Based on the triaxial strength, the relationship between normalized octahedral normal stress σ oct / f c and octahedral shear stress τ oct / f c with RCA replacement ratio and stress ratio was discussed.

The mechanical performance of coral concrete under combined compression-shear stresses was investigated using the multifunctional true triaxial testing machine. The shear load–displacement curves, normal displacement-shear displacement curves, and shear failure modes were obtained. Based on the test results, the shear failure modes, deformation proprieties, peak shear strength, and shear strength components were analyzed. The results show that almost all coral aggregates on the shear failure surface are broken. With the normal stress ratio increasing, the fiction traces and tiny concrete debris on the shear failure surface increase, and the peak shear strength and corresponding shear displacement also increase. The shear strength components include cohesion strength, contact friction strength, and shear dilation strength, where the contact friction strength dominates the shear strength with the existence of normal stress. Based on different stress expressions, five failure criterion models are proposed, where the one based on stress invariant achieves the highest prediction accuracy.

An experimental investigation was conducted to study the crack behavior of beams constructed with Recycled Concrete Aggregate (RCA). This experimental program consisted of 16 beams. The test parameters for this study include RCA replacement ratio and longitudinal reinforcement ratio. The flexural properties and crack behaviors of the beams were evaluated based on present design codes. It is found that the use of RCA does not cause an observable change in the progression of flexural strength and crack pattern. However, results of these statistical tests show that the RCA beams possess a larger crack width compares with the conventional beams.

Twelve beam tests were carried out in order to investigate the bond strength and bond position function between corroded rebar and recycled aggregate concrete (RAC), with the electrochemical method adopted to accelerate steel corrosion. Three recycled coarse aggregate (RCA) replacement percentages (i.e., 0%, 50% and 100%) and 4 expected corrosion crack widths of RAC (i.e., 0 mm, 0.05 mm, 0.3 mm, and 0.6 mm) were considered. Test data was used to calculate the bond stress along the anchorage length, and the influence of both RCA replacement percentages and the corrosion cracking widths on the bond strength and bond position function between the RAC and rebar. The bond position functions for different corrosion levels of reinforced RAC were also established. The results indicated that the ultimate bond strength of reinforced RAC beams decreased overall with an increase of the RCA replacement percentage and corrosion crack width, but that the rate of decline reduced with an increase of RCA and corrosion level. The bond position curve of the reinforced RAC beams was similar to that of natural aggregate concrete (NAC) beams subjected to bending and shear stresses before and after steel corrosion, with a sharp increase of the relative bond stiffness at both anchorage ends, and an almost linear decrease of relative bond stiffness in the range of 0.15–0.85 times the anchorage length. Increasing the RCA substitution rate had little effect on the bond position curves, and the bond distribution became more uniform as the crack widths increased.

Mechanical properties including failure mode, strength, and stress–strain relation of recycled concrete specimens are tested under compression-shear stress state. Replacement ratio of recycled coarse aggregate (RCA), stress ratio of applied compression (σ/ƒcu) and reinforcement ratio ( ρ v ) are designed as the main factors which affect mechanical properties of concrete. The results show that the failure mode is mainly affected by σ/ƒcu, both ρ v and σ/ƒcu take an effect on shear strength, the strength value increases with the ρ v and σ/ƒcu goes up. RCA replacement ratio gives a negative effect on shear strength due to the initial damage initiated in crushing process, the strength value decreases with RCA replacement ratio increases. Appropriate formula has been selected to describe the change of shear strength combined with σ/ƒcu and ρ v under different RCA replacement ratios, and the predicted strength curves match well with the experimental data based on regression analysis. The shear stress–strain curve of the plain concrete is influenced by both σ/ƒcu and RCA replacement ratio, the initial slope and the whole shape of the curve are effected by the two factors, a fitting equation is proposed to describe the shear stress–strain relationship of plain concrete under compression-shear composite stress state.