Study of Raman scattering enhancement method based on optical multiplexing for on-line detection of gas components in strong-impact environments.

On-line gas detection under strong impact such as combustion and explosion is of great significance for understanding the reaction processes. To realize simultaneous on-line detection of various gases under strong impact, an approach based on optical multiplexing for enhancing spontaneous Raman scattering is proposed. A single beam is transmitted several times using optical fibers through a specific measurement point in the reaction zone. Thus, the excitation light intensity at the measurement point is enhanced and the Raman signal intensity is substantially increased. Indeed, the signal intensity can be increased by a factor of ∼10, and the constituent gases in air can be detected with sub-second time resolution, under a 100 g impact.

Isolation and characterization of PoWRKY, an abiotic stress-related WRKY transcription factor from Polygonatum odoratum.

WRKY transcription factors play vital roles in response to biotic and abiotic stresses in plants. As a kind of high value medicinal plant, Polygonatum odoratum has an ability to tolerate various abiotic stresses because of the special growth condition. In current study, a novel WRKY gene from P. odoratum is isolated and compared with homologous sequences from other plants. PoWRKY1 possesses two typical WRKY domains and two C2H2 zinc-finger motifs. Evolutionary analysis indicated that PoWRKY1 is most closely related to WRKY protein from Asparagus officinalis. Expression analysis showed that expression of PoWRKY1 is induced by cold and drought stresses but not salt stress. Overexpression of PoWRKY1 in Arabidopsis improved seed germination and root growth of transgenic plants during cold stress and drought. In addition, super oxide dismutase activity and proline content in transgenic plants increased under cold and drought stresses, whereas malondialdehyde levels and relative electrolyte leakage reduced under similar stress conditions. Taken together, these results showed that PoWRKY1 enhances the tolerance to cold and drought stresses. This study lays a potential foundation to understand the molecular mechanism of tolerance to abiotic stress in P. odoratum.

Novel method for quantitative and real-time measurements on engine combustion at varying pressure based on the wavelength modulation spectroscopy.

The wavelength modulation spectroscopy (WMS) technique has been demonstrated as a powerful and indispensable tool for quantitative and real-time measurements on the combustion process of various industrial devices. However, the varying pressure occurred in the aero-engine combustor significantly affects the accuracy and efficiency of the WMS technique. To address this issue, this work reports a novel method named WMS pressure correction model, which can enable fast signal processing in the measurements at varying pressure. The method was first validated in a heated optical cell, and then applied to the pressure and temperature measurements in an aero-engine combustor. The results show that the new method can efficiently and accurately measure the pressure and temperature at the varying pressure conditions.

"Alkene-to-Alkene" Difunctionalization of Enaminones for the Synthesis of Polyfunctionalized Alkenes by Transition-Metal-Free C-H and C-N Bond Transformation.

The three-component reactions of enaminones, disulfides, and alcohols for the synthesis of polyfunctionalized alkenes have been realized via the C-H and C-N bond transformation on enaminones. The reactions proceed in a novel "alkene-to-alkene" difunctionalization mode without using any transition metal. The application of the alkene products in the synthesis of divergent sulfenyl heteroaryls, including sulfenylated pyrazoles, pyrimidines, and isoxazoles, via simple annulation has also been verified.

Spectral effect of streetlamps on urban trees: A simulated study on tissue water, nitrogen, and carbohydrate contents in maple and oak.

Streetlamps enforce night lighting on urban forest trees, but scarce information is available concerning the ecophysiological performance of street trees under these conditions. In this study, maple (Acer truncatum Bunge) and oak (Quercus mongolica Fisch. ex Ledeb.) seedlings were cultured with simulated exposure to streetlamp spectra in white (red/green/blue, 7.7:1.0:2.2) and red plus blue (RB; red/green/blue, 4.6:0.0:1.0) lights with photosynthetic photon flux rate of 80 µmol m-2 s-1 in a 18-h photoperiod. Nitrogen (N) was loaded through 15 weekly applications to an amount of 80 mg N plant-1 to mimic the mineral N deposition to landscape trees. Variables of biomass, carbohydrate accumulation, N and water contents were rarely found difference between the two LED-spectra treatments for both species. Compared to the un-lighted control, the RB spectrum lowered N concentration in oak seedlings and water content in maple seedlings. The white light spectrum resulted in an increase of starch concentration. Carbohydrate concentration had a positive relationship with biomass and N content across two species but a negative relationship with water content in maple seedlings. Overall, streetlamp-lights imposed effects on tree growth by a prolonged photoperiod instead of specific spectrum. Maple had a strong response of water uptake to streetlamp lighting at the cost of carbohydrate consumption, but oak had scarce demand of water-use for growth.

Revisiting the Enhanced Red Upconversion Emission from a Single ß-NaYF4:Yb/Er Microcrystal By Doping with Mn2+ Ions.

The presence of manganese ions (Mn2+) in Yb/Er-co-doped nanomaterials results in suppressing green (545 nm) and enhancing red (650 nm) upconversion (UC) emission, which can achieve single-red-band emission to enable applications in bioimaging and drug delivery. Here, we revisit the tunable multicolor UC emission in a single Mn2+-doped ß-NaYF4:Yb/Er microcrystal which is synthesized by a simple one-pot hydrothermal method. Excited by a 980 nm continuous wave (CW) laser, the color of the single ß-NaYF4:Yb/Er/Mn microrod can be tuned from green to red as the doping Mn2+ ions increase from 0 to 30 mol%. Notably, under a relatively high excitation intensity, a newly emerged emission band at 560 nm (2H9/2 → 4I13/2) becomes significant and further exceeds the traditional green (545 nm) emission. Therefore, the red-to-green (R/G) emission intensity ratio is subdivided into traditional (650 to 545 nm) and new (650 to 560 nm) R/G ones. As the doped Mn2+ ions increase, these two R/G ratios are in lockstep with the same tunable trends at low excitation intensity, but the tunable regions become different at high excitation intensity. Moreover, we demonstrate that the energy transfer (ET) between Mn2+ and Er3+ contributes to the adjustment of R/G ratio and leads to tunable multicolor of the single microrod. The spectroscopic properties and tunable color from the single microrod can be potentially utilized in color display and micro-optoelectronic devices.