Lateral flow assay for simultaneous detection of multiple mycotoxins using nanozyme to amplify signals.

Co-contamination of multiple mycotoxins produces synergistic toxic effects, leading to more serious hazards. Therefore, the simple, rapid and accurate simultaneous detection of multiple mycotoxins is crucial. Herein, a three-channel aptamer-based lateral flow assay (Apt-LFA) was established for the detection of aflatoxin M1 (AFM1), aflatoxin B1 (AFB1) and ochratoxin A (OTA). The multi-channel Apt-LFA utilized gold­iridium nanozyme to catalyze the chromogenic substrate, which effectively achieved signal amplification. Moreover, the positions and lengths of the complementary sequences were screened by changes in fluorescence intensity. After grayscale analysis, the semi-quantitative results showed that the detection limits of AFM1, AFB1 and OTA were 0.39 ng/mL, 0.36 ng/mL and 0.82 ng/mL. The recoveries of the multiplexed competitive sensors in complex matrices of real samples were 93.33%-97.01%, 95.72%-102.67%, and 106.88%-109.33%, respectively. In conclusion, the assembly principle of the three-channel Apt-LFA is simple, which can provide a new idea for the simultaneous detection of small molecule targets.

A Fast Estimation Method for Direction of Arrival Using Tripole Vector Antenna.

The tripole vector antenna comprises three orthogonal dipole antennas, so it could completely capture all the electric field of the incident electromagnetic (EM) wave. Then, the electric field information could be used to estimate the direction of arrival (DOA) of the EM wave if two conditions are satisfied. One is that there exists only one single EM wave in space. The other is that the EM wave is elliptically or circularly polarized. The new estimation method obtains two snapshot vectors through the output of a tripole antenna and computes their cross-product vector. Furthermore, the direction of the cross-product vector is used to estimate the DOA of the EM wave directly. We analyze the statistical characteristics of the DOA estimation error to prove that the new scheme is an asymptotic unbiased estimation. Furthermore, unlike the existing Multiple Signal Classification (MUSIC)-based algorithms, the proposed approach only need one tripole vector antenna instead of an antenna array. Meanwhile, the new method also outperforms existing MUSIC-based algorithms in the term of computational complexity. Finally, the performance and advantages of the proposed method are verified by numerical simulations.

An enhanced coagulation using a starch-based coagulant assisted by polysilicic acid in treating simulated and real surface water.

In this work, a simple and environmentally-friendly enhanced coagulation, by using a cationic starch-based coagulant (starch-3-chloro-2-hydroxypropyl trimethyl ammonium chloride, St-CTA) coupled with an optimized polysilicic acid (PSA), has been tried to coagulate the kaolin suspensions and humic acid (HA) aqueous solutions, which are used as the simulated sources of inorganic colloidal particles and organic pollutant, respectively, in micro-polluted turbid surface water. Dosing of St-CTA and PSA at the same time is more efficient and more convenient than other two separated feeding methods in this enhanced coagulation process. The synergic coagulation process and mechanism were studied and discussed in detail based on the apparent coagulation performance, floc properties, and zeta potentials of supernatants. St-CTA caused an efficient charge neutralization, i.e. compression of electric double layer of kaolin particles and electrostatic adsorption of HA, followed by an effective netting-bridging effect of PSA, resulting in an improved purification performance. St-CTA with a higher charge density showed better purification performance due to enhanced charge neutralization effect. In addition to simulated water, the validation of this enhanced coagulation process was further confirmed by comparison with a conventional coagulant, polyaluminium chloride, in treating a real surface water. This work thus provides a simple and environmentally-friendly strategy to efficiently purify micro-polluted turbid surface water and further improve the water safety.

Evaluating the effects of the preoxidation of H2O2, NaClO, and KMnO4 and reflocculation on the dewaterability of sewage sludge.

The preoxidation effects of H2O2, NaClO, and KMnO4 on the dewaterability of sewage sludge were compared by analyzing the changes in specific resistance to filtration (SRF), filter cake moisture content (FCMC), extracellular polymeric substance (EPS) fractions and components, and floc properties. The three oxidants varied in oxidation efficiency and exhibited distinctive mechanisms. NaClO not only destroyed sludge flocs and EPSs but also effectively caused cell lysis, resulting in release of a considerable amount of organic matters and subsequently significant deterioration of dewatering performance. The oxidation of H2O2 and KMnO4 was relatively mild and occurred mainly on the outer layers of the sludge flocs and cell-bound EPSs. By contrast, the SRF and FCMC of the sludge conditioned with a low dose of KMnO4 were slightly improved, and a fraction of soluble EPS was compressed because of the coagulation effect of the oxidation product MnO2. The pH of the sludge conditioned with H2O2 and KMnO4 showed no considerable change. Meanwhile, NaClO evidently increased the alkalinity of the sludge because of the hydrolysis effect. After the pH of the NaClO-treated sludge was readjusted to 7.0, the partial protonation efficiency slightly alleviated the deterioration of sludge dewatering performance. The preoxidized sludge was then subjected to reflocculation treatment using FeCl3, polyacrylamide, and a cationic starch-based flocculant, respectively. The combined treatment of preoxidation and reflocculation showed a high dewatering efficiency owing to their synergistic effect.

Insights into the effects of acidification on sewage sludge dewaterability through pH repeated adjustment.

Sludge acidification is a popular and efficient pretreatment method for improving sludge dewaterability. To explore the mechanisms of sludge acidification deeply and provide a theoretical basis for practical application, sewage sludge was repeatedly treated by acidification conditioning. The sludge pH was continuously adjusted from 7.0 to 3.0, then back to 7.0, and to 3.0 again in this study. When the sludge pH returned to a neutral condition, the sludge dewaterability was further deteriorated. However, after the second acidification conditioning, the sludge dewaterability was improved to the same level as that at the first conditioning. These experimental facts were due to two acidification effects. One was that acidification can efficiently destroy the structure of sludge flocs, thereby causing the degradation of extracellular polymeric substances (EPSs) and release of trapped water. Furthermore, some internal EPSs were released into the outer layer. The other was protonation effect, which can effectively compress the released EPSs, especially protein-like matters (PN) therein. These two combined effects caused a good sludge dewaterability. However, the former was irreversible, whereas the latter was reversible. When the pH of acidified sludge was readjusted to 7.0, the protonation effect weakened, thereby the original compressed EPS released into the outer layer of sludge and the PN content in soluble EPS fraction increased near five times, resulting in considerable deterioration of sludge dewaterability. The negative effects of released organic matters by acidification were often concealed and neglected due to protonation, thereby causing the reversal of dewatering performance in practice when the sludge pH was fluctuated.