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In order to stabilize the extinction cross section measurement of a single nanoparticle, we propose to analyze the blurriness parameter of aperture edge images in real time, which provides a feedback to lock the sample position. Unlike the conventional spatial modulation spectroscopy (SMS) technique, a probe beam experiences both the spatial modulation by a piezo stage and the temporal modulation by a chopper. We experimentally demonstrate that the measurement uncertainty is one order magnitude less than that in the previous report. The proposed method can be readily implemented in conventional SMS systems and can help to achieve high stability for sensing based on light extinction by a single nanoparticle, which alleviate the impact from laboratory environment and increase the experimental sensitivity.
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We investigate the time response of plasmonic spatial differentiators based on prism coupling configurations. We show that when the incident light is time-modulated, in addition to the spatial differentiation, the output field is also contributed by the signal derivative with respect to time. To reduce this impact, the incident pulse needs a steady time span, and the shortest steady time span is about 100 fs. We further show that the time modulation does not degrade the resolution of the spatial differentiation. Also, we numerically demonstrate the image processing of edge detection by the plasmonic spatial differentiator, with the time-modulated signal.
RESUMO
BACKGROUND: Tenvermectin A is a new avermectin derivative that has good insecticidal and acaricidal effects. In order to study the resistance of Plutella xylostella to tenvermectin A, a sensitive strain (SS) and a laboratory-selected tenvermectin A-resistant strain (RS, 33.57-fold) were used to evaluate cross-resistance and fitness costs as well as to determine the resistance mechanism. RESULTS: There was no cross-resistance with common pesticides except for moderate cross-resistance with cypermethrin (resistance ratio = 10.26-fold) observed in RS. The activities of metabolic enzymes were measured, and the results showed that mixed function oxidase (MFO) and carboxylate esterase (CarE) in RS increased significantly by 2.92- and 2.86-fold, respectively, compared with SS. In addition, there was no obvious difference in glutathione-S-transferase (GST), which indicated that enhanced MFO and CarE activities may be the main mechanisms of detoxification. In the four typical resistance-related genes, expression of GluCl (4.86-fold), ABCC2 (3.85-fold), and CYP6 (2.94-fold) in RS were significantly promoted, but expression of GST was not. The clone and sequence of the PxGluClα subunit displayed six mutations that could lead to changes in the amino acid residues. CONCLUSION: High suitability related to tenvermectin A resistance was observed in RS, and it was found that the developmental stages of RS were significantly shortened and the survival rate of females was reduced. In addition, the mechanism of resistance to tenvermectin A may be regulated by the glutamate-gated chloride channel, ATP-binding cassette transporter, and MFO. In general, the study of resistance and biochemical mechanisms can provide beneficial and rational information for the management of resistance in P. xylostella. © 2021 Society of Chemical Industry.