Similarity Analysis of Rebar Corrosion under Different Electrochemical Accelerated Method

The concrete cover cracking caused by non-uniform corrosion of reinforcing bar is one of the most important reason for structure service performance degradation. The most widely used electrochemical accelerated corrosion methods include external and internal electrode methods. The reinforcement are used as anode in both methods. The different between two methods is the position of auxiliary. In external electrode method, the auxiliary is set outside the specimen, including three methods, i.e. samples whole/part submerged in saline, samples wrapped by sponge and steel mesh. The electrochemical mechanism of these four accelerated method were analyzed by using the FE software COMSOL. According to the corrosion products distribution characteristic along the rebar circumference, the similarity of electrochemical accelerated and natural corrosion was presented. The results indicated that, rebar corrosion with external electrode method can be regarded as uniform corrosion; the internal electrode method could result in a non-uniform corrosion after optimizing, and the orientation and distance of rebar/electrode are two major influence parameters for accelerated non-uniform corrosion. In addition, based on the corrosion electrochemical principles, a modified internal electrode method was given. The stainless wire was put into the cylinder samples parallel to the rebar as a cathode. In present study, the rapid non-uniform corrosion method can play a positive role in studying the cover cracking process of reinforced concrete

RGD-conjugated gold nanorods induce radiosensitization in melanoma cancer cells by downregulating αvβ3 expression

Background: Melanoma is known to be radioresistant and traditional treatments have been intractable. Therefore, novel approaches are required to improve the therapeutic efficacy of melanoma treatment. In our study, gold nanorods conjugated with Arg-Gly-Asp peptides (RGD-GNRs) were used as a sensitizer to enhance the response of melanoma cells to 6 mV radiation. Methods and materials: A375 melanoma cells were treated by gold nanorods or RGD-GNRs with or without irradiation. The antiproliferative impact of the treatments was measured by MTT assay. Radiosensitizing effects were determined by colony formation assay. Apoptosis and cell cycle data were measured by flow cytometry. Integrin alpha(v)beta(3) expression was also investigated by flow cytometry. Results: Addition of RGD-GNRs enhanced the radiosensitivity of A375 cells with a dose-modifying factor of 1.35, and enhanced radiation-induced apoptosis. DNA flow cytometric analysis indicated that RGD-GNRs plus irradiation induced significant G2/M phase arrest in A375 cells. Both spontaneous and radiation-induced expressions of integrin alpha(v)beta(3) were downregulated by RGD-GNRs. Conclusion: Our study indicated that RGD-GNRs could sensitize melanoma A375 cells to irradiation. It was hypothesized that this was mainly through downregulation of radiation-induced alpha(v)beta(3), in addition to induction of a higher proportion of cells within the G2/M phase. The combination of RGD-GNRs and radiation needs further investigation.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000302718200001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Nanoscience & NanotechnologyPharmacology & PharmacySCI(E)22ARTICLE915-924

Improvement of clavulanic acid production in Streptomyces clavuligerus F613-1 by using a claR-neo reporter strategy

Background: Streptomyces clavuligerus was the producer of clavulanic acid, claR, a pathway-specific transcriptional regulator in S. clavuligerus, positively regulates clavulanic acid biosynthesis. In this study, the promoter-less kanamycin resistance gene neo was fused with claR to obtain strain NEO from S. clavuligerus F613-1. The claR-neo fusion strain NEO was mutated using physical and chemical mutagens and then screened under high concentrations of kanamycin for high-yield producers of clavulanic acid. Results: The reporter gene neo was fused downstreamof claR and used as an indicator for expression levels of claR in strain NEO. After three rounds of continuous treatment and screening, the high-yield clavulanic acid-producing strain M3-19 was obtained. In the shaking flask model, the clavulanic acid titer of M3-19 reached 4.33 g/L, which is an increase of 33% over the titer of 3.26 g/L for the starting strains S. clavuligerus F613-1 and NEO. Conclusions: Our results indicate that neo can be effectively used as a reporter for the expression of late-stage biosynthetic genes when screening for high-yield strains and that this approach has strong potential for improving Streptomyces strains of industrial value

The Effect of the Crosstalk between Photoperiod and Temperature on the Heading-Date in Rice

Photoperiod and temperature are two important environmental factors that influence the heading-date of rice. Although the influence of the photoperiod on heading has been extensively reported in rice, the molecular mechanism for the temperature control of heading remains unknown. This study reports an early heading mutant derived from tissue culture lines of rice and investigates the heading-date of wild type and mutant in different photoperiod and temperature treatments. The linkage analysis showed that the mutant phenotype cosegregated with the Hd1 locus. Sequencing analysis found that the mutant contained two insertions and several single-base substitutions that caused a dramatic reduction in Hd1mRNA levels compared with wild type. The expression patterns of Hd1 and Hd3a were also analyzed in different photoperiod and temperature conditions, revealing that Hd1 mRNA levels displayed similar expression patterns for different photoperiod and temperature treatments, with high expression levels at night and reduced levels in the daytime. In addition, Hd1 displayed a slightly higher expression level under long-day and low temperature conditions. Hd3a mRNA was present at a very low level under low temperature conditions regardless of the day-length. This result suggests that suppression of Hd3a expression is a principle cause of late heading under low temperature and long-day conditions

Glabridin inhibited the spread of polymyxin-resistant Enterobacterium carrying ICEMmoMP63

IntroductionThe role of integrative and conjugative elements (ICEs) in antibiotic resistance in Morganella morganii is unknown. This study aimed to determine whether an ICE identified in the M. morganii genome contributed to the polymyxin resistance.MethodsWhole-genome sequencing was performed followed by bioinformatics analyses to identify ICEs and antibiotic resistance genes. Conjugation assays were performed to analyze the transferability of a discovered ICE. A drug transporter encoded on the ICE was heterogeneously expressed in Escherichia coli, minimum inhibitory concentrations of antibiotics were determined, and a traditional Chinese medicine library was screened for potential efflux pump inhibitors.ResultsAn antibiotic resistance-conferring ICE, named ICEMmoMP63, was identified. ICEMmoMP63 was verified to be horizontally transferred among Enterobacteriaceae bacteria. G3577_03020 in ICEMmoMP63 was found to mediate multiple antibiotic resistances, especially polymyxin resistance. However, natural compound glabridin was demonstrated to inhibit polymyxin resistance.DiscussionOur findings support the need for monitoring dissemination of ICEMmoMP63 in Enterobacteriaceae bacteria. Combined glabridin and polymyxin may have therapeutic potential for treating infections from multi-drug resistant bacteria carrying ICEMmoMP63

Influences of Corrosion Degree and Uniformity on Bond Strength and Cracking Pattern of Cement Mortar and PVA-ECC

Engineered cementitious composites (ECCs), which have a strain-hardening behavior under tension, is widely used for repairing and retrofitting reinforced concrete structures. In such applications, the performance of the bond between the ECC and corroded rebar is critical for the service life prediction of the repaired structures. In this study, the cracking patterns and bond behavior of polyvinyl alcohol (PVA) ECCs (PVA-ECCs) and cement mortar with uniform and nonuniform corroded steel rebars were studied. It was found that the uniform corrosion–induced cracks were randomly distributed, while the nonuniform corrosion–induced cracks were concentrated perpendicular to the most corroded side. The bond strength of PVA-ECC and mortar specimens was independent of the corrosion method. The bond strength of PVA-ECC and mortar specimens both showed a trend of increasing first and then decreasing with the development of corrosion rate. The threshold corrosion rate for mortar specimens was 0.125%, and the threshold corrosion rate of PVA-ECC specimens was 0.922%.This is a manuscript of an article published as Fu, Chuanqing, Rui He, and Kejin Wang. "Influences of Corrosion Degree and Uniformity on Bond Strength and Cracking Pattern of Cement Mortar and PVA-ECC." Journal of Materials in Civil Engineering 35, no. 6 (2023): 04023134.  This material may be found at DOI: 10.1061/JMCEE7.MTENG-14846.  This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. Copyright 2023 American Society of Civil Engineers. Posted with permission

Galvanic Corrosion Study between Tensile-Stressed and Non-Stressed Carbon Steels in Simulated Concrete Pore Solution

The present study investigated the galvanic effect between tensile-stressed and non-stressed carbon steels, in addition to the influence of the tensile stress on the passivation and corrosion behavior of steel in a simulated concrete pore solution. Three different levels of tensile stress, ranging from elastic to plastic stress on the surface, were applied by adjusting the displacement of C-shape carbon steel rings. Different electrochemical measurements including the open circuit potential (OCP), the electrochemical impedance spectroscopy (EIS), the zero-resistance ammetry (ZRA), and the cyclic polarization were performed. Based on the results of EIS, the tensile stress degraded the resistance of the oxide film in moderate frequencies while enhancing the charge transfer resistance in low frequencies during passivation. As corrosion propagated, the stressed steel yielded a similar charge transfer resistance to or an even lower charge transfer resistance than the non-stressed steel, especially in the case of plastic tensile stress. The galvanic effect between the tensile-stressed and non-stressed steels increased the chloride threshold value of the tensile-stressed steel, although the susceptibility to pitting corrosion was exhibited after being corroded

Galvanic Corrosion Study between Tensile-Stressed and Non-Stressed Carbon Steels in Simulated Concrete Pore Solution

The present study investigated the galvanic effect between tensile-stressed and non-stressed carbon steels, in addition to the influence of the tensile stress on the passivation and corrosion behavior of steel in a simulated concrete pore solution. Three different levels of tensile stress, ranging from elastic to plastic stress on the surface, were applied by adjusting the displacement of C-shape carbon steel rings. Different electrochemical measurements including the open circuit potential (OCP), the electrochemical impedance spectroscopy (EIS), the zero-resistance ammetry (ZRA), and the cyclic polarization were performed. Based on the results of EIS, the tensile stress degraded the resistance of the oxide film in moderate frequencies while enhancing the charge transfer resistance in low frequencies during passivation. As corrosion propagated, the stressed steel yielded a similar charge transfer resistance to or an even lower charge transfer resistance than the non-stressed steel, especially in the case of plastic tensile stress. The galvanic effect between the tensile-stressed and non-stressed steels increased the chloride threshold value of the tensile-stressed steel, although the susceptibility to pitting corrosion was exhibited after being corroded

Modeling moisture transport at the surface layer of fatigue-damaged concrete

© 2017 Elsevier Ltd This study investigates the moisture transport at the surface layer of concrete damaged by uniaxial tensile fatigue loading. In particular, a theoretical model for calculating the surface factor of drying concrete was established and verified with laboratory testing. The effect of mix proportion (e.g. water-to-binder ratio, supplementary cementitious materials) and level of fatigue damage on the moisture desorption at the concrete surface were studied. The results show that the surface factor of drying concrete increases as the environmental temperature or wind speed increases, but seldom changes with the mix proportion and fatigue damage. However, the fatigue loads (up to 30% of the ultimate tensile load) can accelerate the concrete surface water transfer by a factor of 1.05–1.60 times in the initial drying process, mainly due to enlarged surface mass transfer area.Link_to_subscribed_fulltex

Advances in Sustainable Concrete System

In recent years, the implementation of a sustainable concrete system has been a great topic of interest in the field of construction engineering worldwide as a result of the large and rapid increase in carbon emissions and environmental problems from traditional concrete production and industry [...