Application of light diffraction theory to qualify the downstream light field modulation property of mitigated KDP crystals

Micro-milling can effectively remove laser damage sites on a KDP (potassium dihydrogen phosphate) surface and then improve the laser damage resistance of the components. However, the repaired KDP surface could cause light propagating turbulence and downstream light intensification with the potential risk to damage downstream optics. In order to analyze the downstream light field modulation caused by Gaussian mitigation pits on KDP crystals, a computational model of the downstream light diffraction based on the angular spectrum theory and the Gaussian repair contour is established. The results show that the phase offset caused by the repaired surface produces a large light field modulation near the rear KDP surface. The modulation generated in the whole downstream light field is greater than that caused by the amplitude change. Therefore, the phase characteristics of the outgoing light could be suggested as a vital research topic for future research on the downstream light field modulation caused by mitigation contours. Significantly, the experimental results on the downstream light intensity distribution have good agreement with the simulation ones, which proves the validity of the established downstream light diffraction model. The phase characterization of the outgoing light is proposed as an evaluation tool in the repair of KDP crystals. The developed analytical method and numerical discrete algorithm could be also applicable in qualifying the repair quality of other optical components applied in high-power laser systems

Radiative thermal switch via metamaterials made of vanadium dioxide-coated nanoparticles

In this work, a thermal switch is proposed based on the phase-change material vanadium dioxide (VO2) within the framework of near-field radiative heat transfer (NFRHT). The radiative thermal switch consists of two metamaterials filled with core-shell nanoparticles, with the shell made of VO2. Compared to traditional VO2 slabs, the proposed switch exhibits a more than 2-times increase in the switching ratio, reaching as high as 90.29% with a 100 nm vacuum gap. The improved switching effect is attributed to the capability of the VO2 shell to couple with the core, greatly enhancing heat transfer with the insulating VO2, while blocking the motivation of the core in the metallic state of VO2. As a result, this efficiently enlarges the difference in photonic characteristics between the insulating and metallic states of the structure, thereby improving the ability to rectify the NFRHT. The proposed switch opens pathways for active control of NFRHT and holds practical significance for developing thermal photon-based logic circuits

Impact of spatial resolution on air quality simulation: A case study in a highly industrialized area in Shanghai, China

AbstractThe air pollution contribution from highly industrialized areas has been a prominent issue in regional air quality control. Particular emphasis on local industrial emissions is necessary to understand the complexity of air pollution over highly industrialized areas. Baoshan District, one of the most important industrialized areas in China and the most competitive steel and iron production base worldwide, was selected as the study area in this work. The WRF/CMAQ modeling system with local emission profile was applied to study the impact of spatial resolution on air quality modeling. The simulation results for SO2, NO, NO2, CO and PM10 at both 3–km and 1–km resolutions were verified by ground level observations. The results showed that the allocation of the emission inventory is improved by using finer resolution grids, which allow the consideration of detailed emission features. The influence of model resolution was more significant for air quality than for meteorology simulation. The relative errors using the finer resolution method ranged from –25% to 59%, an obvious improvement over the error value of 26%–245% obtained using the coarse resolution method. The changing tendencies of air pollutants in urban and rural areas were generally better modeled at finer than coarser resolution. However, the detailed variation in the most heavily polluted areas was still difficult to capture, and the model performance was not evidently improved by the use of a fine resolution. To improve the model performance over highly industrialized areas for future studies, combining the dynamic emission profile with detailed industrial activities and accurate local meteorological fields is suggested

The effect of transforming growth factor-β1 on nasopharyngeal carcinoma cells: insensitive to cell growth but functional to TGF-β/Smad pathway

<p>Abstract</p> <p>Objectives</p> <p>This study explored the response of nasopharyngeal carcinoma cells to TGF-β1-induced growth suppression and investigated the roles of the TGF-β/Smad signaling pathway in nasopharyngeal carcinoma cells.</p> <p>Methods</p> <p>The cells of nasopharyngeal carcinoma cell line CNE2 were treated with TGF-β1. The growth responses of CNE2 cells were analyzed by MTT assay. The mRNA expression and protein subcellular localization of the TGF-β/Smad signaling components in the CNE2 were determined by real time RT-PCR and immunocytochemical analysis.</p> <p>Results</p> <p>We found that the growth of CNE2 cells was not suppressed by TGF-β1. The signaling proteins TβRII, Smad 7 were expressed normally, while Smad2, Smad3, and Smad4 increased significantly at the mRNA level. TGF-β type II receptor and Smad7 had no change compared to the normal nasopharyngeal epithelial cells. In addition, Smad2 was phosphorylated to pSmad2, and the activated pSmad2 translocated into the nucleus from the cytoplasm, while the inhibitory Smad-Smad7 translocated from the nucleus to the cytoplasm after TGF-β1 stimulation.</p> <p>Conclusion</p> <p>The results suggested that CNE2 cells are not sensitive to growth suppression by TGF-β1, but the TGF-β/Smad signaling transduction is functional. Further work is needed to address a more detailed spectrum of the TGF-β/Smad signaling pathway in CNE2 cells.</p

Multiple magnetoplasmon polaritons of magneto-optical graphene in near-field radiative heat transfer

Graphene, as a two-dimensional magneto-optical material, supports magnetoplasmon polaritons (MPP) when exposed to an applied magnetic field. Recently, MPP of a single-layer graphene has shown an excellent capability in the modulation of near-field radiative heat transfer (NFRHT). In this study, we present a comprehensive theoretical analysis of NFRHT between two multilayered graphene structures, with a particular focus on the multiple MPP effect. We reveal the physical mechanism and evolution law of the multiple MPP, and we demonstrate that the multiple MPP allow one to mediate, enhance, and tune the NFRHT by appropriately engineering the properties of graphene, the number of graphene sheets, the intensity of magnetic fields, as well as the geometric structure of systems. We show that the multiple MPP have a quite significant distinction relative to the single MPP or multiple surface plasmon polaritons (SPPs) in terms of modulating and manipulating NFRHT