Inactivation of Edwardsiella tarda and Vibrio harveyi by Chlorination in Seawater

Edwardsiella tarda (E. tarda) and Vibrio harveyi (V. harveyi), common pathogenic bacteria in fish, contribute to elevated mortality rates within fish populations. Chlorination, a widely utilized disinfection method, can effectively manage these microorganisms. The present research examined the impact of chlorination in the inactivation of two microorganisms, with varying pH, chlorine doses, natural organic matter (NOM) concentrations, and temperatures. Microbial inactivation during seawater chlorination is strongly influenced by the formation of chlorine-produced oxidants (CPOs), whose speciation was determined by pH, and concentrations of bromide ions and ammonium ions. At pH 7.1, mixed CPOs (mainly HOBr/NHxBry/NHBrCl) were formed, while NH2Cl was the dominant species at pH 8.2. The higher inactivation efficacies at pH 7.1 compared with those at pH 8.2 were explained by the stronger bactericidal activities of HOBr than NH2Cl. Meanwhile, microbial inactivation was enhanced with increasing chlorine dose and temperature, but it was inhibited with increasing NOM concentration. For a 2 log reduction of E. tarda and V. harveyi, the required concentration–time product (Ct) values were 0.0978 and 0.1102 mg·min/L, respectively, at pH 7.1. These values rose to 0.3644 and 0.3968 mg·min/L, respectively, when the pH increased to 8.2. The Ct values determined in this study provide essential guidelines for safeguarding against microbial contaminants in seawater, thus proposing effective chlorination protocols in aquaculture

Prediction of the Crystal Morphology of β‑HMX using a Generalized Interfacial Structure Analysis Model

At sufficiently low supersaturations such that the spiral growth mechanism dominates, β-cyclotetramethylenetetranitramine (HMX) grows from acetone into a polyhedron surrounded mainly by the (020) and (011) faces. In order to elucidate the morphology, a generalized form of the interfacial structure analysis model is suggested. In this method, the molecular order parameters of crystals are defined to identify the orientation and conformation of the adsorbed growth unit at the interface. This presents a robust method to calculate the orientational and conformational free energy surfaces that are utilized for the spiral growth model of centrosymmetric growth units with polygonal spiral edges. From the metadynamics simulation using these order parameters as collective variables, the free energy surfaces with respect to the collective variables revealed that high conformational free energy of the chair conformation discouraged preordering of the growth units into crystal-like orientation and conformation. The resulting morphology was consistent with the previous experimental and theoretical results, indicating that the anisotropic local concentrations of the growth units at the interface play a critical role in the different relative growth rates of the slow-growing faces

Requirements for Forming Efficient 3‑D Charge Transport Pathway in Diketopyrrolopyrrole-Based Copolymers: Film Morphology vs Molecular Packing

To achieve extremely high planarity and processability simultaneously, we have newly designed and synthesized copolymers composed of donor units of 2,2′-(2,5-dialkoxy-1,4-phenylene)­dithieno­[3,2-<i>b</i>]­thiophene (TT-P-TT) and acceptor units of diketopyrrolopyrrole (DPP). These copolymers consist of a highly planar backbone due to intramolecular interactions. We have systematically investigated the effects of intermolecular interactions by controlling the side chain bulkiness on the polymer thin-film morphologies, packing structures, and charge transport. The thin-film microstructures of the copolymers are found to be critically dependent upon subtle changes in the intermolecular interactions, and charge transport dynamics of the copolymer based field-effect transistors (FETs) has been investigated by in-depth structure–property relationship study. Although the size of the fibrillar structures increases as the bulkiness of the side chains in the copolymer increases, the copolymer with the smallest side chain shows remarkably high charge carrier mobility. Our findings reveal the requirement for forming efficient 3-D charge transport pathway and highlight the importance of the molecular packing and interdomain connectivity, rather than the crystalline domain size. The results obtained herein demonstrate the importance of tailoring the side chain bulkiness and provide new insights into the molecular design for high-performance polymer semiconductors

Interfacial Structure Analysis for the Morphology Prediction of Adipic Acid Crystals from Aqueous Solution

Adipic acid crystals grown from aqueous solutions have a hexagonal plate morphology with a dominant (100) face, where the hydrogen-bonding carboxylic acid groups are exposed. In the present work, the crystal morphology was investigated by interfacial structure analysis to obtain the relative growth rates for the spiral growth model. The concentration of effective growth units at the interface was found to be the key external habit-controlling factor by molecular dynamics simulations at the crystal–solution interface. The differences between the experimentally observed faces of (002), (100), and (011) and unobserved faces of (111̅), (102̅), and (202̅) were explained by two concepts from the interfacial structure analysis that determine the concentration of the effective growth units. The observed faces were characterized by larger values of both the surface scaling factor and molecular orientation factor, implying low anisotropic local concentrations at the interface and high free energy barriers for reorientation on these faces, respectively. Furthermore, the number of turns and the length of one complete spiral rotation and the number of unsaturated bonds were incorporated into the original approach. This consideration of the spiral geometry resulted in a close resemblance to the experimental morphology