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Determining the binding capacity of concrete to chloride ions has always been the focus of the durability study of reinforced concrete structures. In many cases, concrete interior is in the electric field environment, such as railway track affected by stray current, component under electrical chloride removal (ECR), and concrete in corrosion electric field. However, the influence of electric field intensity on the chloride binding ability of concrete has not been determined clearly and quantitatively. In this paper, an experimental study is conducted to investigate the evolution of chloride binding capacity under various electrical current densities. The results indicate that the binding capacity of concrete is degraded by the electrical field, and the amount of physical adsorption for chloride is far less than the that of chemical binding. Based on experimental data, the modified Langmuir isotherm is given, and the evolution of key coefficients is measured quantitatively. The research findings are of great significance to the accurate evaluation of subsequent transmission of chloride ions after the initiation of steel corrosion and corrosion protection effect by ECR technique.

Owing to their surface active properties, surfactants have numerous applications in different fields of life. In the present research work, the solubilization of reactive red 2 (RR2) has been studied in single and mixed micellar systems (MMS) using UV-visible spectroscopy and electrical conductivity measurements. The interaction of RR2 with ionic micelles of cetylpyridinium chloride (CPC) was investigated. In order to probe the interaction of RR2 in MMS, mixtures of CPC and TX-114 (Triton X-114, a nonionic surfactant) were used. UV-visible spectroscopy has been used to obtain the degree of solubilization of RR2 in terms of the partition coefficient (Kc) and Gibbs free energy of partitioning (ΔG°p). Electrical conductivity data have been employed to detect the critical micelle concentration (CMC) of the surfactant systems in the presence of RR2 and, accordingly, to calculate the thermodynamic parameters of the micellization. From the obtained data, it is concluded that the micellization is spontaneous at all studied temperatures. Moreover, the micellization was observed to be driven by both enthalpy and entropy. The results also indicated that MMS have better solubilizing power than single micellar solutions. [ABSTRACT FROM AUTHOR]

The complexation flocculation (CF) method was successfully employed to identify binding coefficients (K doc ) of specific organic contaminants to dissolved organic matter (DOM, often indicated by dissolved organic carbon, DOC) in a multi-contaminant hydrophobic organic contaminant (HOC) system. K doc values were obtained for most of the evaluated 33 HOCs, indicating the feasibility and applicability of the CF method in a multi-contaminant system. Significant positive correlations were observed between binding coefficients and octanol–water partition coefficients (K ow ) for organic halogen compounds, such as polybrominated diphenyl ethers (PBDEs) ( R 2 = 0.95, p < 0.05) and organic chlorine pesticides (OCPs) (methoxychlor excluded, R 2 = 0.82, p < 0.05). The positive correlations identified between the lgK doc and lgBCF (bioconcentration factor) for PBDEs and OCPs, as well as the negative correlation observed for polycyclic aromatic hydrocarbons (PAHs), indicated that different binding or partition mechanisms between PAHs and organic halogen compounds exist. These differences further result in discriminative competition partitions of HOCs between DOM and organisms. Assuming that only freely dissolved HOCs are bioconcentrative, the results of DOM-influenced bioconcentration factor (BCF DOM ) and DOM-influenced lowest observed effect level (LOEL DOM ) indicate that the ecological risk of HOCs is decreased by DOM. [ABSTRACT FROM AUTHOR]

We have performed single-molecule studies of GFP-Lacl repressor proteins bound to bacteriophage χ DNA containing a 256 tandem lac operator insertion confined in nanochannels. An integrated photon molecular counting method was developed to determine the number of proteins bound to DNA. By using this method, we determined the saturated mean occupancy of the 256 tandem lac operators to be 13, which constitutes only 2.5% of the available sites. This low occupancy level suggests that the repressors influence each other even when they are widely separated, at distances on the order of 200 nm, or several DNA persistence lengths. [ABSTRACT FROM AUTHOR]