Evaluation of hidden H2-consuming pathways using metabolic flux-based analysis for a fermentative side-stream dynamic membrane bioreactor using untreated seed sludge

This study investigates the performance and hidden hydrogen consuming metabolic pathways of a fermentative side stream dynamic membrane (DM) bioreactor using flux balance analysis (FBA). The bioreactor was inoculated with untreated methanogenic seed sludge. It was found that fouling rate aggravated with increasing COD concentration (10–30 g/L) and was positively correlated to it rather than to the applied solid flux on the DM module. Due to increased fouling rate the hydraulic retention time (HRT) could not be reduced less than 0.82 ± 0.02 d. An increase in the organic loading rate (OLR) led to an increase in H₂ yield from 0.01 to 0.76 mol H₂/mol of sucrose. FBA revealed that homoacetogenesis was the main H₂-consuming pathway at lower OLRs (corresponding to 10 and 15 g COD/L), while for the OLR corresponding to 30 g COD/L, homoacetogens were suppressed. More importantly, caproic acid production pathway was identified for the first time as another H₂-consuming pathway at high OLR which was not significant at lower OLRs during fermentative dynamic membrane bioreactor operations.     

An Efficient Eco-Friendly Synthesis of Pyran Annulated Heterocyclic Systems under Conventional Heating and Microwave Irradiation in Solvent-Free Conditions

1,4-Diazabicyclo[2.2.2]octane (DABCO) has been used as an efficient and reusable solid base catalyst for the rapid and green synthesis of pyran annulated heterocyclic ring systems by the condensation reaction of various activated CH-acids and tetracyanoethylene under conventional heating and microwave irradiation in solvent-free conditions. Excellent yield, very short reaction time (2–5 min), operatinal simplity, easy work-up procedure, avoidance of hazardous or toxic catalysts, and organic solvents are the main advantages of this green methodology which makes it more economic than the other conventional methods.     

QSAR Study of Antimicrobial 3-Hydroxypyridine-4-one and 3-Hydroxypyran-4-one Derivatives Using Different Chemometric Tools

A series of 3-hydroxypyridine-4-one and 3-hydroxypyran-4-one derivatives were subjected to quantitative structure-antimicrobial activity relationships (QSAR) analysis. A collection of chemometrics methods, including factor analysis-based multiple linear regression (FA-MLR), principal component regression (PCR) and partial least squares combined with genetic algorithm for variable selection (GA-PLS) were employed to make connections between structural parameters and antimicrobial activity. The results revealed the significant role of topological parameters in the antimicrobial activity of the studied compounds against S. aureus and C. albicans. The most significant QSAR model, obtained by GA-PLS, could explain and predict 96% and 91% of variances in the pIC₅₀ data (compounds tested against S. aureus) and predict 91% and 87% of variances in the pIC₅₀ data (compounds tested against C. albicans), respectively.     

Optimal design of a radial-flow membrane reactor as a novel configuration for continuous catalytic regenerative naphtha reforming process considering a detailed kinetic model

The significance of the catalytic naphtha reforming process in the petroleum refining and petrochemical industry generates continuous evolution of the technology. These improvements would be observed in presenting more efficient reactor setups in order to improve production yield and operating conditions, as well as elucidating better kinetic and deactivation models with higher predicting ability. Both of these items have been considered in this work. An optimized radial-flow moving bed membrane reactor has been proposed as a novel configuration for naphtha reforming process. Optimization has been carried out by differential evolution (DE) method considering 40 decision variables. A detailed kinetic model has also been presented. The proposed kinetic model consists of 32 lumped pseudo-components and 84 reactions. Deactivation rate of catalyst has also been taken into account by considering coke deposition on both acidic and metallic sites. Plant data have been used to validate the modeling results. In order to assess the performance of the proposed configuration, the obtained modeling results have been compared with those of conventional configuration, which shows the superiority of the presented one.     

Highly selective and sensitive voltammetric sensor based on modified multiwall carbon nanotube paste electrode for simultaneous determination of ascorbic acid,acetaminophen and tryptophan

A carbon-paste electrode modified with multiwall carbon nanotubes (MWCNTs) was used for the sensitive and selective voltammetric determination of ascorbic acid (AA) in the presence of 3,4-dihydroxycinnamic acid (3,4-DHCA) as mediator. The mediated oxidation of AA at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperommetry and electrochemical impedance spectroscopy (EIS). Also, the values of catalytic rate constant (k), and diffusion coefficient (D) for AA were calculated. Using square wave voltammetry (SWV), a highly selective and simultaneous determination of AA, acetaminophen (AC) and tryptophan (Trp) has been explored at the modified electrode. The modified electrode displayed strong function for resolving the overlapping voltammetric responses of AA, AC and Trp into three well-defined voltammetric peaks. In the mixture containing AA, AC and Trp, the three compounds can well separate from each other with potential differences of 200, 330 and 530 mV between AA and AC, AC and Trp and AA and Trp, respectively, which was large enough to determine AA, AC and Trp individually and simultaneously.     

Morphological and electrical characterization of conductive polylactic acid based nanocomposite before and after FDM 3D printing

Three dimensional (3D) printing holds strong potential for the formation of a new class of multifunctional nanocomposites. Therefore, both the nanocomposites and 3D printing communities need to make more collaborations and innovations for developing and processing of new polymers and composites to get benefit of functionalities of 3D printed nanocomposites. The contribution of this paper is the creation of 3D printable filaments from conductive polymer nanocomposites using a melt mixing process. Multi-walled carbon nanotubes (MWNTs) and high-structured carbon black (Ketjenblack) (KB) were incorporated into polylactic acid. The percolation threshold of MWNT composites is 0.54 wt % and of KB composites is 1.7 wt % by four-point resistance measurement method. In the similar melt mixing process, there was no dependence of diameter of produced 3D printer filaments on the MWNT loading, instead the diameter was dependent on the KB loading and increased with increasing the filler amount. The conductivity of extruded filaments from 3D printer in low filler contents decreases with increasing extruder temperature, yet in higher filler contents there is no effect of extruder temperature on conductivity. Finally, the resistance decreases exponentially with the increase of cross-sectional area of 3D printed tracks. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47040.