Molecular-Scale Study of Salicylate Adsorption and Competition with Catechol at Goethite/Aqueous Solution Interface

Insights into the adsorption mechanisms of salicylate on goethite, especially its competition with catechol, can further our understanding of the fate and transport of natural organic matter analogues in the environment. The adsorption process was investigated using multiple complementary techniques including batch adsorption experiments, flow-cell ATR-FTIR measurement, and DFT calculations. The macroscopic results show that increasing pH and ionic strength had an adverse effect on salicylate adsorption because of electrostatic interactions. Salicylate formed an inner-sphere complex in a mononuclear monodentate configuration with carboxylate bound to the iron atom on goethite surface within pH 5–9. The electrostatic outer-sphere complex could be observed under high salicylate concentrations and low ionic strength. In the competitive adsorption of salicylate and catechol, their individual interfacial complexes coexisted and competed with each other. The surface salicylate could be replaced by catechol during adsorption under neutral and basic pH conditions. Accordingly, the macroscopic adsorption capacity of salicylate was depressed in the binary system

Bacterial Diversity in Linglong Gold Mine, China

<p>Bacteria have been actively regulating cycles of various elements in the environment. To explore the potential bacterial role in gold biogeochemical cycling, this study analyzed the bacterial diversity of mine rock (MR) and surface soil (SS) samples from Linglong gold mine using 16S rRNA gene clone library analysis and cultivation method. From MR, 24 operational taxonomic units (OTUs) were identified from MR, covering 3 phyla and 18 genera. Meanwhile, 24 OTUs were identified from SS, including 4 phyla and 18 genera. Compared with 16S rRNA gene clone library analysis, 28 aerobic and 34 anaerobic isolates were obtained, whereas 26 aerobic and 71 anaerobic strains were isolated from SS. The cultivable bacteria were affiliated with Firmicutes, Proteobacteria and Actinobacteria phyla, and dominated by Firmicutes. These results underscore the high level of bacterial diversity in the gold mine. Our study provides information on the microbial diversity in Linglong gold mine and sheds light on the existence and potential function of bacteria in the gold biogeochemical cycling.</p

Editorial: The combination of data-driven machine learning approaches and prior knowledge for robust medical image processing and analysis

Editorial: The combination of data-driven machine learning approaches and prior knowledge for robust medical image processing and analysis</p

Insights from Arsenate Adsorption on Rutile (110): Grazing-Incidence X‑ray Absorption Fine Structure Spectroscopy and DFT+U Study

Insights into the bonding of As­(V) at the metal oxide/aqueous interface can further our understanding of its fate and transport in the environment. The motivation of this work is to explore the interfacial configuration of As­(V) on single crystal rutile (110) using grazing-incidence X-ray absorption fine structure spectroscopy (GI-XAFS) and planewave density functional calculations with on-site repulsion (DFT+U). In contrast to the commonly considered corner-sharing bidentate binuclear structure, tetrahedral As­(V) binds as an edge/corner-sharing tridentate binuclear complex on rutile (110), as evidenced by observation of three As–Ti distances at 2.83, 3.36, and 4.05 Å. In agreement with the GI-XAFS analysis, our DFT+U calculations for this configuration resulted in the lowest adsorption energy among five possible alternatives. In addition, the electron density difference further demonstrated the transfer of charge between surface Ti atoms and O atoms in AsO₄. This charge transfer consequently induced the formation of a chemical bond, which is also confirmed by the partial density of states analysis. Our results may shed new light on coupling the GI-XAFS and DFT approaches to explore molecular-scale adsorption mechanisms on single crystal surfaces

Insights into Propranolol Adsorption on TiO₂: Spectroscopic and Molecular Modeling Study

Insights from molecular-level mechanisms of propranolol adsorption can further our understanding of the fate and transport of beta blockers in the environment. The motivation of our study is to explore the dynamic adsorption process of propranolol at the TiO₂/aqueous interface on the molecular scale. Multiple complementary techniques including macroscopic adsorption experiments, flow-cell ATR-FTIR measurement, XPS, and quantum chemical calculations were used to study the adsorption mechanisms. Our results show that propranolol adsorption on TiO₂ increased from 0.3 to 2.3 μmol/g in the pH range 5 to 9. The ATR-FTIR and XPS analysis indicated that the hydroxyl and amino groups of propranolol strongly interacted with the TiO₂ surface. The DFT calculations suggested the molecular structure of surface complexes with hydrogen bonding and the charge transfer from propranolol to TiO₂ surface upon adsorption

Comparison of cell counting and developmental stage classification (Objective 20X).

<p>Comparison of cell counting and developmental stage classification (Objective 20X).</p

Comparison of parasitemia values using image-based cytometer and flow cytometer.

<p>Mixed stage malaria parasites were diluted in hRBCs to obtain parasitemia ranging between 0.2% and 9% and scored using image-based cytometer. The results were comparable with flow cytometer values with no significant difference. The figure represents the average of three independent measurements performed and the error bars represent the standard deviation of the average values.</p

Images automatically analyzed by the developed image-based cytometer.

<p>(A) Original image taken by objective 20X. (B) Representation of all the extracted RBCs. (C) Extracted schizont stage iRBCs. (D) Extracted trophozoite stage iRBCs.</p

Comparison of dose response curves for the three antimalarial drugs generated using image-based cytometer and flow cytometer.

<p>Well-known anti-malarials; (A) Chloroquine, (B) Artemisinin and (C) Cycloheximide were screened against the laboratory strain, 3D7. Standard growth inhibition assay was performed and IC₅₀ values determined using our image-based cytometer and flow cytometry in parallel [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179161#pone.0179161.t003" target="_blank">Table 3</a>], to obtain comparable results. The error bars represent standard errors.</p

Comparison of cell counting and developmental stage classification (Objective 20X).

<p>Comparison of cell counting and developmental stage classification (Objective 20X).</p