Multi-Criteria Decision Analysis for Optimizing CO2 and NH3 Removal by Scenedesmus dimorphus Photobioreactors

Numerous technologies have been investigated for mitigating air pollutant emissions from swine barns. Among them, algal photobioreactors (PBRs) can remove and utilize air pollutants such as CO2 and NH3 from barn exhaust. However, a challenge to PBR operation is that it involves multiple system input parameters and output goals. A key question is then how to determine the appropriate CO2 and NH3 concentrations in this case. Conventional statistical methods are inadequate for handling this complex problem. Multi-criteria decision-making (MCDM) emerges as a practical methodology for comparison and can be utilized to rank different CO2–NH3 interactions based on their environmental and biological performance. By employing MCDM methods, producers can effectively control the ratio of CO2 and NH3 concentrations, enabling them to identify the optimal range of operating parameters for various housing types, ensuring efficient pollutant mitigation. In this study, a multi-criteria decision-making (MCDM) approach was employed to support operation management. Specifically, influent CO2 and NH3 concentrations were optimized for three scenarios (the best biological, environmental, and overall performance), using a combination of two MCDM techniques. This study is anticipated to facilitate the system analysis and optimization of algae-based phytoremediation processes

DDA simulation study on fracturing failure reproducibility of heterogenous rock

The mesoscale heterogeneity of rock determines its macroscale mechanical performance to a large extent. In this paper, a sub-block element discontinuous deformation analysis (DDA) method coupled with a statistic heterogeneity model was used to simulate the fracturing failure of pre-notched rock specimens. The simulation recreated the macroscale whole-process nonlinear deformation and fracturing failure of pre-notched disc and rectangular specimens with some important features explored in experiments or other numerical simulations. Combing intact heterogeneous rock specimen simulations in previous work, the effect of the heterogeneity on the reproducibility of macroscale strength and failure patterns of the specimens were investigated. Results indicate that the influence degree of the heterogeneity on the macroscale equivalent strength and fracturing failure pattern reproducibility varies with the specimen particularities (disc or rectangular, pre-notched or intact, and inclination of the pre-existing flaw), and the reason behind was discussed from the point view of stress concentration. This work is meaningful for the understanding of the result discreteness of rock specimen experiments, and assures the importance to consider the rock heterogeneity in practical rock engineering

Feasibility of coupling a thermal/optical carbon analyzer to a quadrupole mass spectrometer for enhanced PM2.5 speciation

A thermal/optical carbon analyzer (TOA), normally used for quantification of organic carbon (OC) and elemental carbon (EC) in PM2.5 (fine particulate matter) speciation networks, was adapted to direct thermally evolved gases to an electron impact quadrupole mass spectrometer (QMS), creating a TOA-QMS. This approach produces spectra similar to those obtained by the Aerodyne aerosol mass spectrometer (AMS), but the ratios of the mass to charge (m/z) signals differ and must be remeasured using laboratory-generated standards. Linear relationships are found between TOA-QMS signals and ammonium (NH4+), nitrate (NO3-), and sulfate (SO42-) standards. For ambient samples, however, positive deviations are found for SO42-, compensated by negative deviations for NO3-, at higher concentrations. This indicates the utility of mixed-compound standards for calibration or separate calibration curves for low and high ion concentrations. The sum of the QMS signals across all m/z after removal of the NH4+, NO3-, and SO42- signals was highly correlated with the carbon content of oxalic acid (C2H2O4) standards. For ambient samples, the OC derived from the TOA-QMS method was the same as the OC derived from the standard IMPROVE_A TOA method. This method has the potential to reduce complexity and costs for speciation networks, especially for highly polluted urban areas such as those in Asia and Africa.Implications: Ammonium, nitrate, and sulfate can be quantified by the same thermal evolution analysis applied to organic and elemental carbon. This holds the potential to replace multiple parallel filter samples and separate laboratory analyses with a single filter and a single analysis to account for a large portion of the PM2.5 mass concentration

Cyclic di-GMP regulates bacterial colonization and further biocontrol efficacy of Bacillus velezensis against apple ring rot disease via its potential receptor YdaK

Bacillus species are among the most investigated beneficial bacteria and widely used in agricultural systems as biological control agents. Its biocontrol efficacy is controlled by diverse regulators. Cyclic diguanylate (c-di-GMP) is a nearly universal second messenger in bacteria and modulates various important physiological processes, including motility, biofilm formation, antifungal antibiotic production and host colonization. However, the impact of c-di-GMP on biocontrol efficacy of beneficial bacteria is unknown. Bacillus velezensis PG12 is an effective biocontrol strain against apple ring rot disease caused by Botryosphaeria dothidea. In this study, the contribution of c-di-GMP to biocontrol efficacy of B. velezensis PG12 was investigated. Deletion of single gene encoding diguanylate cyclase or phosphodiesterase did not affect its biocontrol efficacy against apple ring rot. However, artificial modulation of c-di-GMP level in the cells leads to a significant change of biocontrol efficacy, suggesting that c-di-GMP positively regulates biocontrol efficacy of B. velezensis PG12 against apple ring rot disease. More evidences indicate that c-di-GMP does not affect the antagonistic activity of B. velezensis PG12 against B. dothidea in vitro and in vivo, but positively regulates biofilm formation of B. velezensis PG12 and its colonization on apple fruits. Importantly, deletion of ydaK could rescue the inhibition of biofilm formation, bacterial colonization and biocontrol efficacy caused by low c-di-GMP level, indicating that YdaK is the potential c-di-GMP receptor to regulate biofilm formation, colonization and effective biological control. However, YdaK did not affect the antagonistic activity of B. velezensis PG12 against B. dothidea. Based on these findings, we propose that c-di-GMP regulates biofilm formation, subsequently the bacterial colonization on apple fruits and thus biocontrol efficacy of B. velezensis through its receptor YdaK. This is the first report showing that c-di-GMP plays a role in biocontrol efficacy of beneficial bacteria