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Generators are typically dispatched in a preventive way to guarantee frequency stability in any single generator trip contingency. The largest generator outage is regarded as the severest by the conventional N-1 frequency security rule, since the contingency size is often the dominating factor in traditional systems. However, with the continuous integration of renewable energy sources and fast response devices (e.g., battery), the inertia and frequency response characteristics of generators become diversified. In such situations, the largest generator cannot be simply identified as the bottleneck generator for preventive dispatch, since the post-contingency frequency dynamic is determined by both the contingency size and the frequency response ability of the remaining system. In this paper, a system's frequency response ability (FRA) is quantitatively defined and derived as a function of system intrinsic parameters (e.g., system inertia, ramp rates of generators, load frequency relief coefficient, etc.). Then, the bottleneck generator can be identified through comparing the capacity of a unit with the maximum FRA of its corresponding remaining system. On this basis, an innovative N-1 frequency security constrained optimal intraday generator dispatch scheme is correspondingly established. Simulation results verify the superiority of the proposed method in both frequency security improvement and operation cost saving.

In this study, a novel magnetic separation-based multiple systematic evolution of ligands by exponential enrichment (SELEX) was applied to select aptamers simultaneously against three kinds of marine biotoxins, including domoic acid (DA), saxitoxin (STX), and tetrodotoxin (TTX). Magnetic reduced graphene oxide (MRGO) was prepared to adsorb unbound ssDNAs and simplify the separation step. In the multiple SELEX, after the initial twelve rounds of selection against mixed targets and the subsequent four respective rounds of selection against each single target, the three resulting ssDNA pools were cloned, sequenced, and analyzed. Several aptamer candidates were selected and subjected to the binding affinity and specificity test. Finally, DA-06 (Kd= 62.07 ± 19.97 nM), TTX-07 (Kd= 44.12 ± 15.38 nM), and STX-41 (Kd= 61.44 ± 23.18 nM) showed high affinity and good specificity for DA, TTX, and STX, respectively. They were also applied to detect and quantify DA, TTX, and STX successfully. The other two multitarget aptamers, DA-01 and TTX-27, were also obtained, which can bind with either DA or TTX. These aptamers provide alternative recognition molecules to antibodies for biosensor applications.

In this study, a highly sensitive and specific multiplex chemiluminescent method for the simultaneous detection of three antibiotics was fabricated. Thiolated hybridized complementary strand (cDNA) modified N-(4-aminobutyl)-N-ethylisoluminol (ABEI) functionalized flowerlike gold nanostructures (AuNFs) were used as signal probes. Oxytetracycline (OTC), tetracycline (TET) and kanamycin (Kana) aptamers that were fixed onto the bottom of microtiter plates were used as recognition molecules. Targets and signal probes can competitively combine with the fixed aptamers. Thus, OTC, TET and Kana can be simultaneously detected based on an ABEI–H2O2–P-iodophenol (PIP) steady-state chemiluminescence (CL) system and the CL intensity is related to the negative logarithm of the concentrations of OTC/TET/Kana, respectively. The ranges are 0.05 to 5 ng mL−1, 0.05 to 5 ng mL−1, and 0.005 to 0.5 ng mL−1, and the detection limits are 0.02, 0.02 and 0.002 ng mL−1(S/N = 3), respectively. The capability of the bioassay in milk was also studied using the standard addition recovery method, and the results showed a good consistency with the ones that were obtained from a commercial ELISA method. Owing to the advantages of a simple operation procedure, and excellent selectivity and specificity, the proposed biosensor demonstrated great potential in the application of food safety and multiplex nanosensors.

Ochratoxin A (OTA) contamination of corn has received significant attention due to the wide distribution and high toxicity of OTA. The maximum residue limit standard of OTA in corn has been established by the Chinese Government and other unions. Nanoparticle-based fluorescence resonance energy transfer (FRET) assays are promising methods for the sensitive and fast detection of OTA. However, satisfactory detection sensitivity is commonly achieved with complicated signal amplification processes or specific nanoparticle morphologies, which means that these assays are not conducive to fast detection. This study proposes a simple and novel strategy to improve the sensitivity of FRET aptasensors. In this strategy, a DNA tetrahedron was first used in gold nanorod-based FRET aptasensors. DNA tetrahedron-modified gold nanorods are used as fluorescent acceptors, and Cy5-modified complementary sequences of the OTA aptamer are used as fluorescent donors. The aptamers of OTA are embedded in the DNA tetrahedrons, and FRET occurs when the aptamers hybridize with the Cy5-modified complementary sequences. The aptamer-integrated DNA tetrahedron modified on the surface of gold nanorods acts as an anchor, thus avoiding the crowding and entanglement of aptamers. Due to the competitive combination between the OTA aptamers and complementary sequences, the greater the amount of OTA, the less the amount of Cy5-modified complementary sequences that bind with the aptamers and the less the amount of Cy5 that is quenched. Thus, the fluorescence intensity is positively related to the OTA concentration. In this study, in the concentration range of 0.01–10 ng/mL, the fluorescence intensity was found to be linearly related to the logarithmic concentration of OTA. The limit of detection was calculated to be 0.005 ng/mL. The specificity of the developed biosensor was demonstrated to be efficient. The accuracy and stability of the developed aptasensor were also tested, and the method exhibited good performance in real samples.