Synthesis and Antifungal Activity of Coumarin Derivatives Containing Hydrazone Moiety.

Plant disease control mainly relies on pesticides. In this study, a series of coumarin derivatives containing hydrazone moiety were designed and synthesized. The synthesized compounds were characterized and used to evaluate the antifungal activity against four pathogens, Botrytis cinerea, Alternaria solani, Fusarium oxysporum, and Alternaria alternata. The results showed that the inhibition rate of some compounds at 100 µg/mL in 96 hours reached around 70 % against A. alternata, higher than that of the positive control. The corresponding EC50 values were found at around 30 µg/mL. Finally, the compound 3 b was screened out with the lowest EC50 value (19.49 µg/mL). The analysis of SEM and TEM confirmed that the compound 3 b can obviously damage the morphological structure of hyphae, resulting in the depletion of the cells by the destruction of morphological matrix and leakage of contents. RNA sequencing showed that compounds 3 b mainly affected the pentose phosphate pathway, which caused to destroy the layer of mitochondrial structure. Molecular docking showed that compounds 3 b fitted the binding pocket of yeast transketolase and interacted with lysine at the hydrazone structure. Our results suggested that the introduction of hydrazone was an effective strategy for the design of novel bioactive compounds.

A high-performance cell-phone based polarized microscope for malaria diagnosis.

We present a cell-phone based polarized microscope for diagnosing malaria through hemozoin recognition over a wide field-of-view (FOV) accompanied with decent image performance. The system is constructed based on attachment method using a lens assembly as objective, two mobile phones and two linear polarizers. A ~0.92 µm resolution across a FOV of ~3.27 mm × 3.27 mm with high imaging quality is realized, demonstrating an increased resolving power, four times improvement in FOV and better imaging quality over mobile-optical-polarization imaging device. Importantly, we also demonstrate it has capability of recognizing hemozoin within the sample for malaria diagnosis by imaging malaria-infected blood samples with similar sensitivity comparable to Leica microscopy. It is more compact, portable, and insensitive to alignment, making it highly suitable for malaria detection in a portable, easy to setup and use way in low-resource areas.

A wide-field microscope utilizing two cellphones for health-care applications.

In this report, we report a wide field-of-view (FOV) bright field (BF) microscope with compact and portable optical components, mechanically attached to the existing camera unit of the cellphone. A white screen displayed on a cellphone as the illumination source to pump the sample of interest uniformly for the purpose of the reduction in assembly complexity and alignment. It offers a large FOV of 4.36 × 3.27 mm without digital zoom and a spatial resolution of 1.5 µm. Furthermore, we also have demonstrated the potential application for diseases diagnosis and screening by imaging malaria-infected blood sample and iron deficiency anemia blood sample in resource-constrained settings where mobile phone infrastructure is already ubiquitous but microscope is notoriously scarce.

Fast differential discrimination approach to improve time resolution with multiple returns for time-of-flight system.

A differential discrimination approach has been proposed in this paper to make fast discrimination from multi-returns in time-of-flight (TOF) systems. The time resolution of classical direct discrimination in a laser TOF system has been analyzed. A theoretical model of the differential discriminator has been established. As theoretical calculations and numerical simulations have shown, time resolution can be improved by using a differential discriminator instead of a classical direct discriminator, especially with large-amplitude signals. However, the relationship between the time resolution and the amplitude is not monotonic. The time resolution decreases as the amplitude decreases when the signals are small. But, through further analysis and simulations, a method to find an appropriate parameter, which can optimize the relationship curve, has been proposed. The theory and the simulations were verified by electrical circuit experiments, and the optical circuit experiments taken with two close targets of about 8.3 m. The FWHM of the laser is about 1.9 ns. The measured time resolution was better than 2.2 ns when the amplitude is 30 mV.

Interference effect from noise on range-gated laser ranging and tracking system.

Influence of high-repetition-rate noise on a range-gated laser ranging and tracking system (LRTS) is studied both theoretically and experimentally. The interference mechanism of high-repetition-rate noise on range gates is revealed. The interference effect, especially the effect caused by relative shift between signal and noise, is presented through theoretical analysis and numerical simulation. In order to verify the simulation model, both electrical closed circuit and optical circuit experiments are further conducted. Both the simulation model and experiment results show that both periodic and nonperiodic noise pulses can enter the range gates of a LRTS and affect its operation with both their high repetition rate and relative shift to echo pulses.

Single laser free-space duplex communication system with adaptive threshold technique and BER analysis in weak turbulent atmosphere.

A free space duplex communication system with a single laser and a modulated retro-reflector is presented. A method to minimize the echo wave bit error rate (BER) of this system is proposed by setting the optimum threshold automatically based on the measured mean power and irradiance variances with log-normal distribution and the Bayes minimum classification error criterion. Experiments were taken at a distance of 1.55 km in a weak turbulence and the measured BER was 0.0213. The BER performance of this system is studied and the result shows the experimental BER is in good accordance with the theoretical value.