The Effect of Initial Water Saturation on Freeze-thaw Damage of Submerged Mortar Materials

An indispensable condition for the occurrence of the freeze-thaw (F-T) damage in unsaturated cement-based materials is that the specimens absorb water during the F-T process and reach a critical level of water saturation, which is influenced by the initial degree of water saturation (IDWS). However, the fast-freeze method commonly used in the laboratory does not reflect the effect of the IDWS on F-T damage. Thus, this study investigated the effect of different IDWS on the development of F-T damage in specimens to fill the gap in this research area. In this study, compressive strength tests were used to characterize the development of damage, while SEM and MIP tests were used to identify the damage at a microscopic level. A reasonable explanation for the damage development was suggested using the critical satiation theory as well as the negative-temperature pumping effect. According to the experimental and discussed results, damage developed more rapidly in specimens with a low IDWS compared to specimens with a high IDWS. The rapid development of damage was not only related to the hydrostatic pressure during the F-T process, but also the osmotic pressure generated during the entry of external water. As the IDWS decreased, the negative-temperature pumping effect of the specimens became more pronounced. Therefore, a lower IDWS led to a higher osmotic pressure caused by the entry of external water and faster development of damage. This, in return, created more water transfer paths and accelerated the process of reaching the critical level of water saturation, significantly weakening the F-T resistance of the specimen

Research on the corrosion/permeability/forest resistance of concrete by experimental and microscopic mechanisms under different water-binder ratios

To study the influence of different water–binder ratios on the corrosion, permeability, and freezing properties of concrete, we produced different strengths of concrete with respective water–binder ratios of 0.32, 0.38, 0.50, and 0.66. The corrosion resistance of the concrete was studied via three corrosion methods: full immersion, half immersion, and dry and wet cycles. The impermeability and frost resistance of concrete with different water–binder ratios were tested and analyzed. The test results show that the corrosion modes in order from strong to weak were dry and wet cycles, half soaking, and full soaking. The relative dynamic elasticity modulus and freeze–thaw index were used to evaluate the frost resistance of concrete based on the analysis of three indices of frost resistance. To study the internal mechanism of corrosion of concrete with different water–binder ratios, microscopic pore structure testing of the concrete was conducted using a Micromeritics AutoPore IV 9500 Series instrument. The porosimeter studies show that the smaller the water–binder ratio, the more small pores and the denser the concrete. The smaller the water–binder ratio, the higher the strength and the better the corrosion, permeability, and frost resistance

Vacancy-Mediated Magnetism in Pure Copper Oxide Nanoparticles

Room temperature ferromagnetism (RTF) is observed in pure copper oxide (CuO) nanoparticles which were prepared by precipitation method with the post-annealing in air without any ferromagnetic dopant. X-ray photoelectron spectroscopy (XPS) result indicates that the mixture valence states of Cu1+ and Cu2+ ions exist at the surface of the particles. Vacuum annealing enhances the ferromagnetism (FM) of CuO nanoparticles, while oxygen atmosphere annealing reduces it. The origin of FM is suggested to the oxygen vacancies at the surface/or interface of the particles. Such a ferromagnet without the presence of any transition metal could be a very good option for a class of spintronics

Resource structuring or capability building? An empirical study of the business value of information technology

This paper examines two ways to create business value of information technology (BVIT): resource structuring and capability building. We develop a research model positing that IT resources and IT capabilities enhance a firm\u27s performance by providing support to its competitive strategies and core competencies, and the strengths of these supports vary in accord with environmental dynamism. The model is empirically tested using data collected from 296 firms in China. It is found that IT resources generate more business effects in stable environments than in dynamic environments, while IT capabilities generate more business effects in dynamic environments than in stable environments. The results suggest that the BVIT creation mechanism in stable environments is primarily resource structuring while the mechanism in dynamic environments is primarily capability building. © 2012 M.E. Sharpe, Inc. All rights reserved

Screening and Analysis of Antifungal Strains <i>Bacillus subtilis</i> JF-4 and <i>B. amylum</i> JF-5 for the Biological Control of Fusarium Wilt of Banana

Purpose: This study aimed to identify the antagonistic bacteria from the rhizosphere of healthy bananas that can effectively suppress the Fusarium wilt of banana, and to further investigate the inhibitory mechanism. Method: The primary and secondary screening techniques were implemented using the double-plate and fermentation antagonism methods. The strain was identified based on physiological and biochemical tests, 16S rRNA gene sequencing, and specific gene amplification. The effects of crude extract on the protein content, lipid peroxidation, and pectinase activity of mycelia were determined from the identified isolates. Results: Two antagonistic bacteria, JF-4 and JF-5, were screened and initially identified as Bacillus subtilis (GenBank: OR125631) and B. amylum (GenBank: OR125632). The greenhouse experiment showed that the biological control efficiency of the two antagonists against the Fusarium wilt of banana was 48.3% and 40.3%, respectively. The catalase content produced by lipid peroxidation increased significantly after treatment with the crude extracts of JF-4 and JF-5 at concentrations of 0.69 μmol/L and 0.59 μmol/L, respectively. The protein and ergosterol content and pectinase activity decreased significantly. The two antagonistic bacteria might inhibit the growth of pathogens by enhancing lipid peroxidation and decreasing the synthesis of cell metabolites. Twenty compounds were identified by gas chromatography–mass spectrometry (GC-MS). B. subtilis JF-4 was further sequenced and assembled to obtain a complete circular chromosome genome of 681,804,824 bp. The genome consisted of a 4,310,825-bp-long scaffold. Conclusion: The findings of this study may help elucidate the mechanism behind this biocontrol isolate