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This study presents an experimental method for investigating the compressive creep behavior of C-S-H micropillars at micro-scale. The micropillars with two different diameters (5 μm and 0.5 μm) in hardened cement paste (HCP) are fabricated using focused ion beam (FIB) milling and subjected to compression using an indenter with flat-end tip. Multi-stage loading protocols are used to sequentially obtain the elastic modulus, creep behavior, and compressive strength of the individual C-S-H micropillar sample. The sinking effect of C-S-H micropillars during the compression introduces a part of irrelevant deformation to the displacement measured by the indenter. To address this, a numerical procedure is used to quantify the sinking deformation and to determine the true stress-strain relationship of the C-S-H micropillar from the measured indentation force-displacement relationship. The results show that the measured specific creep compliance of all C-S-H micropillars can be well described by power-law functions with an average R2 > 0.99. In contrast, if the specific creep curves are fitted by logarithmic functions, the average R2 is only 0.59. It is indicated that the micropillar creep tests capture the short-term creep of C-S-H. Moreover, micropillar creep tests measure the creep compliance of C-S-H that is one order of magnitude faster than the most macroscopic creep tests. This experimental study emphasizes the impact of imposed stress status on the creep behavior of C-S-H at microscale. [ABSTRACT FROM AUTHOR]

• Exceptional properties of developed Ultra-High Performance Concrete (UHPC). • Structural design considerations for UHPC overlay on concrete bridge. • Construction techniques for successful UHPC overlay implementation. As ultra-high performance concrete (UHPC) has superior mechanical and durability properties, it is a promising solution to apply a thin layer of UHPC on top of normal concrete bridge decks to extend the service life and enhance the structure integrity. However, the large autogenous shrinkage characteristics of UHPC is still an issue, and there is a lack of research focus on the structural design and stress analysis of the concrete bridge deck and UHPC overlay system. Thus, this study first designs and evaluates a new low-shrinkage UHPC mixture internally cured with a high-strength, high-abrasion resistant, and porous aggregate (calcined bauxite, CB), and the optical mixture design is validated by testing the fresh, mechanical, autogenous shrinkage, abrasion, and impact properties of the UHPCs. Second, the outdoor UHPC overlay-NC composite slab experiments and the numerical modeling are carried out to analyze the shrinkage performance of the UHPC, debonding potential of the overlay layer, stress and strains development in the system. Then, the significant influencing factors and the key measures to assure the UHPC-NC interface bonding properties are obtained, including proposing a grouped L-shape steel rebar arrangement for strengthening the interface. Finally, the applicability of the new low-shrinkage UHPC mixture as overlay materials on a real concrete bridge deck is demonstrated. Based on these, the engineering design scheme and the construction recommendations of an environmentally-cured low-shrinkage UHPC overlay on concrete bridge deck is given. The utilization of UHPC overlay on concrete bridge decks offers a novel paving system that substantially enhances strength, abrasion resistance, and durability. [ABSTRACT FROM AUTHOR]

• Grouped L-shape rebar connectors can alleviate UHPC delamination from NSC substrate. • Grouped connectors can increase the degree of restraint to UHPC overlay by 13%∼38%. • The bond-slip behavior of these L-shape rebar connectors is evaluated by simulation. Ultra-high performance concrete (UHPC) overlay deployed in concrete bridge deck pavement exhibits a high amount of shrinkage that can lead to warping and debonding from the substrate of normal-strength concrete (NSC). This paper is to use grouped L-shape rebar connectors as a solution to alleviate the warping and debonding of the UHPC overlay which is cast on the NSC substrate. The rebar connectors are designed to be post-installed vertically in the hardened NSC substrate, and the rest part of the connectors are anchored in the UHPC overlay after the UHPC casting. In this study, an outdoor UHPC-NSC composite slab test was carried out, and two types of UHPC materials with distinct autogenous shrinkage were produced to cast the overlay. Different schemes of the rebar connector layout with various installing rates were performed. The restrained shrinkage of the UHPC overlay was monitored by the embedded strain sensors, and the UHPC overlay's long-term warping behavior was evaluated. In addition, a numerical model was established considering the shrinkage and creep of UHPC, the contact between the UHPC and the NSC substrate, and the concrete-to-rebar interaction. The results show that the grouped L-shape steel rebar connectors significantly affect the restrained shrinkage of the UHPC overlay by increasing the degree of restraint to the UHPC overlay by 13%-38%. The grouped L-shape steel rebar connectors are proven effective in alleviating warping and delamination in the UHPC-NSC composite slabs. Therefore, the use of grouped rebar connections is feasible in bridge deck pavement engineering. [ABSTRACT FROM AUTHOR]

Ultra-high performance concrete (UHPC) shows very different properties such as high level of autogenous shrinkage and low creep coefficient compared to conventional concrete. One of the problems posed by this is that when UHPC is used as a thin, bonded overlay for concrete bridge decks or pavements, there is limited information regarding the shrinkage-induced warping of the overlay and optimization designs to minimize it. This study conducted a hygro-mechanical finite element analysis to investigate the warping behavior of UHPC overlay cast on mature substrate of normal strength concrete (NSC). The simulation results were validated with the observations from outdoor overlay tests. It is shown that incorporating the shrinkage and creep of UHPC and the bonding behavior of the overlay-to-substrate interface can predict the UHPC overlay's warping deformation in an accurate way. Based on the model, a parametric study was carried out to investigate the influences of sealed curing period, the roughness degree (the bond strength) of overlay/substrate interface, the overlay thickness, the rebar reinforcement inside the overlay, and the amount of total (free) shrinkage of UHPC on the magnitude of the overlay's warping. The findings obtained in this study include the following: (1) The UHPC's shrinkage and the bond strength between UHPC overlay and substrate are two essential factors affecting the overlay's warping behavior, (2) With an increase in UHPC overlay thickness, the calculated overlay's warping deformation is slightly increased, and (3) Internal rebar reinforcement has a limited contribution to reduce the overlay's warping. [ABSTRACT FROM AUTHOR]

• The pore parameters are measured from MIP, BSE, and X-ray CT scanning techniques. • The pore characteristics of cement pastes subject to freeze-thaw cycles are assessed. • The intrinsic permeability of cement paste is obtained by three different methods. • The GEM method is a more suitable tool for cementitious materials with low porosity. Assessing the permeability of concrete subject to unexpected freeze-thaw cycles at early age is critical to ensure the durability and service life of concrete structures. However, measuring permeability of concrete and cement paste has been a challenge. In this study, the intrinsic permeability of cement paste is calculated by using Katz-Thompson equation, general effective media (GEM) method, and Navier-Stokes method based on the pore parameters measured from the mercury intrusion porosimetry (MIP), the backscattered electron (BSE) imaging, and the X-ray computed tomography (CT) techniques. The pastes are subject to freeze-thaw cycles at the age of 1 and 7 days followed by sealed curing until the age of 40 days. The water-to-cement (w/c) ratios of paste are 0.3 and 0.5, representing the high- and low-strength concrete, respectively. The measured pore characteristics and the calculated intrinsic permeability are then compared to that of the control samples. The measurable pore size range of each technique is quantified, and the applicability of each computing method for permeability is discussed. The results of this study provide the insight into the feasibility of different measuring techniques for pore parameters and the predicting methods for permeability, particularly for cementitious materials subject to freeze-thaw cycles. [ABSTRACT FROM AUTHOR]

Highlights • RF exposure reduced testosterone levels and its synthesis genes in mice testis. • RF exposure reduced levels in CamkI/Rorα mRNA/protein expression. • KN-93 blocked the inhibitory effect of RF exposure on testosterone synthesis and regulatory factors of CamkI and Rorα in primary Leydig cells. • Ionomycin reversed the down-regulation effect of RF exposure on intracellular [Ca2+]i and CamkI/Rorα mRNA/protein expression in vitro. Abstract Exposure to radiofrequency fields (RF) has been reported to induce adverse effects on testosterone production and its daily rhythm. However, the mechanisms underneath this effect remain unknown. In this study, male mice were exposed to 1800 MHz radiofrequency fields (RF, 40 μW/cm2 power intensity and 0.0553 W/Kg SAR) 2 h per day for 32 days. The data suggested that RF exposure: (i) significantly reduced testosterone levels, (ii) altered the expression of genes involved in its synthesis (Star, P450scc, P450c17 and 3β-Hsd) in testicular tissue, (iii) significantly reduced regulatory protein CaMKI/ROR α. Similar observations were also made in cultured primary Leydig cells exposed in vitro to RF. However, all of these observations were blocked by CaMK inhibitor, KN-93, and ionomycin reversed the down-regulation effects on intracellular [Ca2+]i and CaMKI/ROR α expression induced by RF exposure. Thus, the data provided the evidence that RF-induced inhibition of testosterone synthesis might be mediated through CaMKI/ROR α signaling pathway. Capsule: CaMKI/RORα signaling pathway was involved in the inhibition of testosterone synthesis induced by RF exposure. [ABSTRACT FROM AUTHOR]

Assessing the stress development in concrete requires an appropriate tensile creep model which is capable of incorporating the effect of the field environment conditions. This study quantifies the effect of temperature variation on the very early-age stress developments in restrained concrete by adopting a modified microprestress-solidification (MPS) theory-based creep model. The MPS creep model is first calibrated and verified based on the measured direct tensile creep data under normal and high temperature histories, it is then used to predict the very early-age stress development of the fully restrained concrete specimens under variable temperature history since casting. The predicted results are in good agreement with the experimental results. The tensile stress in restrained specimens can be relaxed by 80 %–87% within the first three days since casting. The predicted stress exhibits an obvious deviation from the measured one if temperature effect is not considered. Therefore, it is of importance to consider the temperature effect on concrete creep when the temperature variation in concrete is significant, and MPS creep model is valid for tensile stress prediction in concrete at very early ages. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new method of Direct Friction Stir Processing is proposed to fabricate Mg/SiCp surface composite like a planter. [•] The tool was designed as a hollow and pinless tool, and the reinforcement were preplaced. [•] The reinforcement particles were homogeneous and dispersed in the stir zone. [•] The micro-hardness and wear property were promoted by refinement crystallization and reinforcement particles. [ABSTRACT FROM AUTHOR]

Hyporheic zone is an important region of nitrogen removal in river systems. Hyporheic exchange generally leads to heterogeneous redox environments, which are conducive to nitrogen transformation. This study seeks to determine the influence of hyporheic upwelling fluxes on inorganic nitrogen (NH 4 + , NO 3 − , and NO 2 − ) concentrations in the sediment pore water of the Weihe River, China. The patterns and magnitudes of hyporheic water exchange on 12 August 2016 were derived by a one-dimensional heat transport model, and inorganic nitrogen concentrations in the pore water, surface water, and groundwater were obtained. The results indicated that hyporheic water exchange was characterized by upwelling at each point during the test period. Moreover, NH 4 + dominated the hyporheic zone from 0 to 45 cm, likely due to organic nitrogen mineralization. Additionally, a non-linear relationship was observed between NH 4 + concentrations and upwelling fluxes. This relationship was derived by analyzing the effect of upwelling on biogeochemical activity and nitrogen transformation. Notably, increasing upwelling fluxes less than 400 mm/d resulted in high NH 4 + concentrations, whereas fluxes exceeding 400 mm/d led to low NH 4 + concentrations. Overall, the variations in inorganic nitrogen associated with hyporheic water exchange are of great importance for controlling nitrogen pollution and maintaining sustainable health in river systems. [ABSTRACT FROM AUTHOR]

The aim of the present study was to elucidate whether the GATA-4/SF-1 signalling pathway is involved in the inhibitory effects of melatonin on testosterone production in both the TM3 Leydig cell line and in C57BL/6J mice. In-vitro experiments demonstrated that melatonin treatment significantly reduced testosterone levels in cell culture medium ( P < 0.05 or P < 0.01); and decreased intracellular cyclic adenosine monophospha accumulation ( P < 0.05 or P < 0.01) and mRNA/protein expression of GATA-4 , SF-1 (NR5A1) , StAR , P450SCC (CYP11A1) and 3β-HSD ( P < 0.05 or P < 0.01). These effects were blocked by N-acetyl-2-benzyltryptamin, a melatonin receptor antagonist. Similar effects of melatonin on testosterone production ( P < 0.05 or P < 0.01) and down-regulation of transcription factors GATA-4 and SF-1 ( P < 0.01) were also observed in mice treated with intratesticular injections of melatonin. Overall, the data suggest that the inhibitory effects of melatonin on testosterone production are mediated via down-regulation of GATA-4 and SF-1 expression. [ABSTRACT FROM AUTHOR]

Abstract: An approach for fabrication of core–shell composite beads was described, with polystyrene–divinylbenzene (PS–DVB) as the core and multi-walled carbon nanotubes (MWCNTs) as the shell through electrostatic attraction-induced self-assembly. MWCNTs were easily quaternized with a defined number of bonded layers and desirable positive charge by a multi-step synthesis, using methylamine and 1,4-butanediol diglycidyl ether as monomers to build a branching polymer that has quaternary ammonium groups. PS–DVB beads were sulfonated by sulfuric acid to provide opposite charge, which had electrostatic interaction with quaternized MWCNTs. Functionalization of MWCNTs was characterized by techniques that include Fourier transform infrared spectroscopy, thermogravimetry and scanning electron microscopy. The dispersion of MWCNTs in deionized water was enhanced after the grafting of cationic polyelectrolytes on them, which was in agreement with the positive charge at any pH value. With the PS–DVB/MWCNT composite beads as anion exchange phase and potassium hydroxide solutions as eluent, the common inorganic anions were well separated with high stability. [Copyright &y& Elsevier]

Abstract: A single pump cycling-column-switching technique has been developed for the iodate analysis in edible salt. Homemade high exchange capacity columns were adopted for the separation of iodate and chloride. Iodate could be retained and concentrated in a homemade concentrator column after eluents passing through the suppressor. With UV detection, iodate exhibited satisfactory linearity in the range of 0.1–10.0mg/L with a correlation coefficient of 0.9996. The detection limit (LOD) was 45.53μg/L, based on the signal-to-noise ratio of 3 (S/N =3) and a 100μL injection volume. Relative standard deviations (RSDs) for retention time, peak area and peak height were all less than 2.1%. Recoveries of added iodate were in the range of 98.4–101.6% for the spiked samples. The quantitative determination of iodate in edible salt was accomplished by this column-switching technique, without any pretreatment and interference. The results on six samples were statistically compared with results determined by conventional titrimetric method. [Copyright &y& Elsevier]

Ex situ nitrification and sequential in situ denitrification represents a novel approach to nitrogen management at landfills. Simultaneous ammonia and organics removal was achieved in a continuous stirred tank reactor (CSTR). The results showed that the maximum nitrogen loading rate (NLR) and the maximum organic loading rate (OLR) was 0.65gNl−1 d−1 and 3.84gCODl−1 d−1, respectively. The ammonia and chemical oxygen demand (COD) removal was over 99% and 57%, respectively. In the run of the CSTR, free ammonia (FA) inhibition and low dissolved oxygen (DO) were found to be key factors affecting nitrite accumulation. In situ denitrification was studied in a municipal solid waste (MSW) column by recalculating nitrified leachate from CSTR. The decomposition of MSW was accelerated by the recirculation of nitrified leachate. Complete reduction of total oxidized nitrogen (TON) was obtained with maximum TON loading of 28.6gNt−1 TSd−1 and denitrification was the main reaction responsible. Additionally, methanogenesis inhibition was observed while TON loading was over 11.4gNt−1 TSd−1 and the inhibition was enhanced with the increase of TON loading. [Copyright &y& Elsevier]