Surface-modified activated carbon for N-nitrosodimethylamine removal in the continuous flow biological activated carbon columns.

The carcinogenic nitrogenous disinfection by-product, N-nitrosodimethylamine (NDMA), is challenging to adsorb due to its high polarity and solubility. Our previous research demonstrated that the adsorptive removal of NDMA can be improved using surface-modified activated carbon (AC800). The current study evaluated the efficacy of AC800 in removing NDMA in a continuous-flow column over 75 days, using both granular activated carbon (GAC) and biologically activated carbon (BAC) columns. The AC800 GAC column demonstrated extended breakthrough and exhaustion times of 10 days and 22 days, respectively, compared to the conventional GAC column at 4 days and 10.5 days. The surface modification effect persisted for 25 days before the removal trends became indistinguishable. The AC800 BAC column outperformed the conventional BAC column with a longer breakthrough time of 11.3 days compared to 7.4 days. BAC columns consistently showed greater NDMA removal, emphasizing the role of biodegradation in NDMA removal on carbon. The higher NDMA removal in the inoculated columns was attributed to increased microbial diversity and the dominance of six specific genera, Methylobacterium, Phyllobacterium, Curvibacter, Acidovorax, Variovorax, and Rhodoferax. This study provides new insights into using modified activated carbon as GAC and BAC media in a real-world continuous-flow setup.

Near-Thermal Reactions of Au+(1S,3D) and AuX+ with CH3X (X = Br, I): A Combined Experimental and Computational Analysis.

Reactions of Au+(1S,3D) and AuX+ with CH3X (X = I and Br) were performed in the gas phase by utilizing a selected-ion drift cell reactor. These experiments were done at room temperature as well as reduced temperature (∼200 K) at a total pressure of 3.5 Torr in helium. Rate coefficients, product sequencing, and branching fractions were obtained for all reactions to evaluate reaction efficiencies and higher-order processes. Reactions of both Au+ states proceed with moderate efficiencies as compared to the average dipole orientation model with these neutral substrates. Results from this work revealed that, dependent on the reacting partner, Au+(1S) exhibits, among others, halogen abstraction, HX elimination, and association. By comparison, Au+(3D) participates primarily in charge transfer and halogen abstraction. Dependent on the halogen ligand, AuX+ ions induce several processes, including association, charge transfer, halogen loss, and halogen substitution. AuI+ reacting with CH3Br resulted in association exclusively, whereas the AuI+/CH3I and AuBr+/CH3Br systems exhibited halogen loss as the dominant process. By contrast, all possible bimolecular pathways occurred in the reaction of AuBr+ with CH3I. Observed products indicate that displacement of bromine by iodine on gold is favored in ionic products, consistent with the thermochemical preference for formation of the Au+-I bond. All AuX+ reactions proceed at maximum efficiency. Potential energy surfaces calculated at the B3LYP/def2-TZVPP level of theory for the AuX+ reactions are in good agreement with the available thermochemistry for these species and with previously calculated structures and energetics. Experimental and computational results are consistent with a mechanism for the AuX+/CH3Y systems where bimolecular products occur either via direct loss of the halogen originally on Au or via a common intermediate resulting from methyl migration in which the Au center is three-coordinate.

MinION Sequencing of colorectal cancer tumour microbiomes-A comparison with amplicon-based and RNA-Sequencing.

BACKGROUND: Recent evidence suggests a role for the gut microbiome in the development and progression of many diseases and many studies have been carried out to analyse the microbiome using a variety of methods. In this study, we compare MinION sequencing with meta-transcriptomics and amplicon-based sequencing for microbiome analysis of colorectal tumour tissue samples. METHODS: DNA and RNA were extracted from 11 colorectal tumour samples. 16S rRNA amplicon sequencing and MinION sequencing was carried out using genomic DNA, and RNA-Sequencing for meta-transcriptomic analysis. Non-human MinION and RNA-Sequencing reads, and 16S rRNA amplicon sequencing reads were taxonomically classified using a database built from available RefSeq bacterial and archaeal genomes and a k-mer based algorithm in Kraken2. Concordance between the three platforms at different taxonomic levels was tested on a per-sample basis using Spearman's rank correlation. RESULTS: The average number of reads per sample using RNA-Sequencing was greater than 129 times that generated using MinION sequencing. However, the average read length of MinION sequences was more than 13 times that of RNA or 16S rRNA amplicon sequencing. Taxonomic assignment using 16S sequencing was less reliable beyond the genus level, and both RNA-Sequencing and MinION sequencing could detect greater numbers of phyla and genera in the same samples, compared to 16S sequencing. Bacterial species associated with colorectal cancer, Fusobacterium nucleatum, Parvimonas micra, Bacteroides fragilis and Porphyromonas gingivalis, were detectable using MinION, RNA-Sequencing and 16S rRNA amplicon sequencing data. CONCLUSIONS: Long-read sequences generated using MinION sequencing can compensate for low numbers of reads for bacterial classification. MinION sequencing can discriminate between bacterial strains and plasmids and shows potential as a cost-effective tool for rapid microbiome sequencing in a clinical setting.

Systematic Ligand Effects in the Reactions of Fe+(6D) and FeX+(5Δ) with CF3X (X = Cl, Br, I). Ion Mobility Measurements of FeX+(5Δ) (X = F, Cl, Br, I) in He.

The gas phase reactions of Fe+(6D) and FeX+(5Δ) with CF3X (X = Cl, Br, I) were examined using a selected-ion drift cell reactor under near-thermal energetic conditions. All reactions were carried out in a uniform electric field at a total pressure of 3.5 Torr at room temperature. In addition, reduced zero-field mobilities were measured for FeX+(5Δ) (X = F, Cl, Br, I) in He, yielding values of 14.2 ± 0.4, 13.7 ± 0.3, 13.3 ± 0.2, and 13.0 ± 0.3 cm2·V-1·s-1, respectively. Fe+(6D) reacts slowly with CF3Cl and CF3Br, producing an adduct exclusively with the former and FeBr+ with the latter. Conversely, Fe+(6D) exhibits efficient chemistry with CF3I to yield FeI+, FeCF3+, and FeFI+ in parallel reactions. Dependent on the halogen, FeX+(5Δ) reactions display one or more of four different processes: F- abstraction, X- abstraction, halogen switching, and association. In general, the presence of the halogen ligand enhances the rate of reaction over that of Fe+(6D) with the same molecular substrate. With CF3Cl, this ligand effect is observed to vary systematically with the electron-withdrawing capability of the halogen. This is illustrated by the correlation between reaction efficiency and the charge distribution on FeX+(5Δ) as determined from DFT calculations. Specific reaction outcomes for the FeX+(5Δ) reactions lead to upper and lower bounds on XFe-Y bond strengths (X, Y = F, Cl, Br, I) that are generally consistent with one another and with known trends.

State-Specific Reactions of Cu(+)((1)S,(3)D) with SF6 and SF5Cl.

State-specific reactions of Cu(+)((1)S,(3)D) were carried out in a selected ion drift cell apparatus with SF6 and SF5Cl. Copper ions were prepared in a glow discharge utilizing Ne as the working gas. Analysis of Cu(+) states using ion mobility mass spectrometry (IMS) indicated the presence of both Cu(+)(3d(10)) and Cu(+)(3d(9)4s(1)) configurations attributable to the (1)S ground and (3)D first excited states of this metal ion, respectively. State-specific product formation in reactions of these ions with the two neutral substrates of interest here was determined using IMS along with both known and calculated energetic requirements for product formation. These experiments indicate that Cu(+)((1)S) associates with both SF6 and SF5Cl; however, the process is approximately four times as efficient with the latter neutral under these conditions. Association is also observed as a minor product between Cu(+)((3)D) and both neutral reactants. Inefficient formation of SF3(+) occurs as the sole bimolecular product from SF6 via Cu(+)((3)D). In contrast, Cu(+)((3)D) reacts with SF5Cl in rapid parallel bimolecular processes yielding SF3(+) and CuCl(+). These results also indicate that CuCl(+) initiates additional higher-order processes which result in SF5(+) and SF4Cl(+). The energetics associated with the formation of SF3(+) suggest that a copper halide neutral byproduct must also be formed, requiring a more complex mechanism than simple dissociative charge-transfer.

State-specific reactions of Cu(+)((1)S,(3)D,(1)D) with the super greenhouse gas SF5CF3.

State-specific reactions of the potent greenhouse gas SF5CF3 with Cu(+) were carried out in a selected ion drift cell apparatus. Copper ions were prepared in a glow discharge utilizing Ne as the working gas. Analysis of these ions using ion mobility mass spectrometry (IMS) indicated the presence of both Cu(+)(3d(10)) and Cu(+)(3d(9)4s(1)) configurations. Subsequent analysis indicates that the 3d(10) configuration consists of Cu(+)((1)S) exclusively whereas the 3d(9)4s(1)configuration is composed primarily of Cu(+)((3)D) with small contributions from Cu(+)((1)D). State-specific product formation in reactions of these ions with SF5CF3 was determined using IMS along with the known energetic requirements for product formation. These experiments reveal that Cu(+) excited states initiate fragmentation of SF5CF3 to yield SF2(+), SF3(+), SF5(+), and CF3(+), where SF3(+) represents the largest branching fraction at 90% of the total bimolecular product formation. The energetics associated with the formation of these ions suggest that molecular Cu-containing products must also be formed in all cases, indicating that the governing reaction mechanisms are more complicated than simple dissociative charge transfer. Production of SF2(+) and SF3(+) are shown to proceed via Cu(+)((3)D) and can be rationalized with a two-step mechanism proceeding through the common intermediate SF3CF3(+). Production of CF3(+) can be explained using this same mechanism but is also energetically possible from Cu(+)((1)D) in a more direct process. Energetic requirements indicate that Cu(+)((1)D) is the sole source of SF5(+) with concomitant formation of CuCF3. Cu(+)((1)S) exhibits adduct formation exclusively, but IMS spectra of the resulting Cu(+)·SF5CF3 suggest that as many as three association structures are formed.

State-specific reactions of Cu(+)(1S, 3D) with CH3X and CF3X (X = Cl, Br, I): exploring the influence of dipole orientation on association and C-X bond activation.

The reactions of gas-phase Cu(+)((1)S) and Cu(+)((3)D) with CF(3)X and CH(3)X (X = Cl, Br, and I) have been examined experimentally using the drift cell technique at 3.5 Torr in He at room temperature. State-specific product channels and overall bimolecular rate constants for depletion of the two Cu(+) states were determined using electronic state chromatography. The results showed that Cu(+)((1)S) participates exclusively in association with all of these neutrals, whereas, depending on the neutral, Cu(+)((3)D) initiates up to three bimolecular processes, resulting in the formation of CuX(+), CuC(H/F)(3)(+), and C(H/F)(3)X(+). Possible structures for the singlet association products were explored using density functional methods. These calculations indicated that Cu(+) preferentially associates with the labile halogen (Cl, Br, I) with all neutrals except CF(3)Cl, for which a "backside" geometry occurs in which Cu(+)((1)S) is weakly bound to the -CF(3) end of the molecule. All products observed on the triplet reaction surface can be understood in terms of either known or calculated thermochemical requirements. Product distributions and overall reaction efficiencies for C-X bond activation (X = Br, I) through Cu(+)((3)D) suggest that the orientation of the neutral dipole has little or no effect in controlling access to specific product channels. Likewise, second-order rate constants for reactions with X = Br and I indicate efficient depletion of Cu(+)((3)D) and do not exhibit the dramatic variations in reaction efficiency previously observed with CH(3)Cl and CF(3)Cl. These results suggest that C-X bond activation proceeds through a bond-insertion mechanism as opposed to direct abstraction.

Near-thermal reactions of Au(+)(1S,3D) with CH3X (X = F,Cl).

Reactions of Au(+)((1)S) and Au(+)((3)D) with CH(3)F and CH(3)Cl have been carried out in a drift cell in He at a pressure of 3.5 Torr at both room temperature and reduced temperatures in order to explore the influence of the electronic state of the metal on reaction outcomes. State-specific product channels and overall two-body rate constants were identified using electronic state chromatography. These results indicate that Au(+)((1)S) reacts to yield an association product in addition to AuCH(2)(+) in parallel steps with both neutrals. Product distributions for association vs HX elimination were determined to be 79% association/21% HX elimination for X = F and 50% association/50% HX elimination when X = Cl. Reaction of Au(+)((3)D) with CH(3)F also results in HF elimination, which in this case is thought to produce (3)AuCH(2)(+). With CH(3)Cl, Au(+)((3)D) reacts to form AuCH(3)(+) and CH(3)Cl(+) in parallel steps. An additional product channel initiated by Au(+)((3)D) is also observed with both methyl halides, which yields CH(2)X(+) as a higher-order product. Kinetic measurements indicate that the reaction efficiency for both Au(+) states is significantly greater with CH(3)Cl than with CH(3)F. The observed two-body rate constant for depletion of Au(+)((1)S) by CH(3)F represents less than 5% of the limiting rate constant predicted by the average dipole orientation model (ADO) at room temperature and 226 K, whereas CH(3)Cl reacts with Au(+)((1)S) at the ADO limit at both room temperature and 218 K. Rate constants for depletion of Au(+)((3)D) by CH(3)F and CH(3)Cl were measured at 226 and 218 K respectively, and indicate that Au(+)((3)D) is consumed at approximately 2% of the ADO limit by CH(3)F and 69% of the ADO limit by CH(3)Cl. Product formation and overall efficiency for all four reactions are consistent with previous experimental results and available theoretical models.

Reactions of Cu+(1S, 3D) with CH3Cl, CH2ClF, CHClF2, and CClF3.

The reactions of gas-phase Cu+(1S) and Cu+(3D) with CH3Cl, CH2ClF, CHClF2, and CClF3 are examined using the drift cell technique at 3.5 Torr. State-specific product channels and overall bimolecular rate constants for depletion of the two Cu+ states are determined using electronic state chromatography. Cu+(1S) participates exclusively in association with all four neutrals, whereas Cl abstraction is the dominant product channel for Cu+(3D). The resulting CuCl+ product subsequently abstracts Cl- in a secondary process. Tertiary reactions are also observed, which include both hydride abstraction (with CH3Cl) and fluoride abstraction (with the fluorinated neutrals). All product channels can be understood in terms of the known thermochemical and quantum mechanical (i.e., spin) requirements. Cu+(1S) is depleted by all four neutrals at 30% to 40% of the ADO rate under these conditions, whereas Cu+(3D) is observed to react at approximately 80% of the ADO rate with CH3Cl, CH2ClF, and CHClF2. Reaction of excited state Cu+ with CClF3 occurs at only 7% of the ADO rate. The behavior of Cu+(3D) is consistent with a mechanism in which formation of CuCl+ occurs exclusively on the triplet surface via a mechanism in which the metal ion must interact exclusively with Cl.