Selective oxidation of methane to methanol in oleum over Pd/C catalyst

The selective oxidation of methane to methanol over Pd/C catalysts generated from a PdCl2, precursor was investigated in oleum. Characterization of the catalysts was performed by X-ray diffraction, X-ray photo-electron spectroscopy, high-resolution transmission electron microscopy, and CO adsorption. The major product ill the oxidation reaction was methyl bisulfate, which was then hydrolyzed into methanol. Methane conversion of 23.6% with methanol selectivity of 69.5% and yield of 16.4% was achieved under the optimum conditions of 5% Pd/C, 30 mu mol Pd, reatction temperature 180 degrees C, methane pressure 4. 0 MPa, reaction time 4 h, and 50% sulfur trioxide concentration. After facile separation with the reactants and pretreatment, the catalyst could be reused several times with considerable stability. The selective oxidation of methane catalyzed by Pd/C catalysts in oleum possibly involved an electrophilic substitute mechanism. The catalystic performance was related to the Pd loading, dispersion, and particle size

Novel integrated strategies toward efficient and stable unassisted photoelectrochemical water splitting

© 2020 Unassisted photoelectrochemical (PEC) water splitting for hydrogen evolution has been regarded as a sustainable route for the harvest and utilization of solar energy. To achieve such unassisted PEC water splitting, two novel integrated strategies have been developed: to design tandem structures of photoanodes/photocathodes and to construct hybrid devices of solar/PEC cells. Some key unsolved problems, however, still limit the further development of high-performance unassisted PEC water splitting, such as low efficiency, poor stability, and high cost. Herein, we present a brief summary of the latest development in this area and propose perspectives for further enhancing this state-of-the-art solar-to‑hydrogen conversion technology, including all-metal oxide photoelectrodes, nanoarray design, surface modification, device coupling, monolithic configuration, and multi-integration

Effects of Dielectric Relaxation on the Director Dynamics of Uniaxial Nematic Liquid Crystals

The dielectric anisotropy of liquid crystals causes director reorientation in an applied electric field and is thus at the heart of electro-optic applications of these materials. The components of the dielectric tensor are frequency dependent. Until recently, this frequency dependence was not accounted for in a description of director dynamics in an electric field. We theoretically derive the reorienting dielectric torque acting on the director, taking into account the entire frequency spectrum of the dielectric tensor. The model allows one to include the effects of multiple relaxations in both parallel and perpendicular components of the dielectric tensor, thus generalizing a recent model [Y. Yin et al., Phys. Rev. Lett. 95, 087801 (2005)] limited by the single-relaxation approach. The model predicts the "dielectric memory effect" (DME)-i.e., dependence of the dielectric torque on both the "present" and "past" values of the electric field and the director. The model describes the experimentally observed director reorientation in the case when the rise time of the applied voltage is smaller than the dielectric relaxation time. In typical materials such as pentylcyanobiphenyl (5CB), in which the dielectric anisotropy is positive at low frequencies, the DME slows down the director reorientation in a sharply rising electric field, as the sharp front is perceived as a high-frequency excitation for which the dielectric anisotropy is small or even of a negative sign. In materials that are dielectrically negative, the DME speeds up the response when a sharp pulse is applied.</p

Effect of Mst1 on Endometriosis Apoptosis and Migration: Role of Drp1-Related Mitochondrial Fission and Parkin-Required Mitophagy

Background/Aims: Mitochondrial homeostasis is implicated in the development and progression of endometriosis through poorly defined mechanisms. Mst1 is the major growth suppressor related to cancer migration, apoptosis and proliferation. However, whether Mst1 is involved in endometriosis apoptosis and migration via regulating the mitochondrial function remains to be elucidated. Methods: Expression of Mst1 in endometriosis was examined via western blots. Cellular apoptosis was detected via MTT and TUNEL assay. Gain of function assay about Mst1 was conducted via adenovirus over-expression. Mitochondrial functions were evaluated via mitochondrial membrane potential JC-1 staining, ROS flow cytometry analysis, mPTP opening assessment and immunofluorescence of HtrA2/Omi. The mitophagy activity were examined via western blots and immunofluorescence. Results: First, we found that Mst1 was significantly downregulated in the ectopic endometrium of endometriosis compared to the normal endometrium. However, the recovery of Mst1 function was closely associated with the inability of endometrial stromal cells (ESCs) to migrate and survive. A functional study indicated that regaining Mst1 enhanced Drp1 post-transcriptional phosphorylation at Ser616 and repressed Parkin transcription activity via p53, leading to mitochondrial fission activation and mitophagy inhibition. Excessive Drp1-related fission forced the mitochondria to liberate HtrA2/Omi into the cytoplasm. Moreover, Mst1-induced defective mitophagy evoked cellular oxidative stress, energy metabolism and calcium overload. Through excessive mitochondrial fission and aberrant mitophagy, Mst1 launched caspase 9-related mitochondrial apoptosis and abrogated F-actin/lamellipodium-dependent cellular migration. Notably, we also defined NR4A/miR181c as the upstream signal for Mst1 dysfunction in endometriosis. Conclusion: Collectively, our results comprehensively described the important role of the NR4A-miR181c-Mst1 pathway in endometriosis, which handled mitochondrial apoptosis and F-actin/ lamellipodium-based migration via the regulation of Drp1-related mitochondrial fission and Parkin-required mitophagy, with a potential application in endometriosis therapy by limiting ESCs migration and promoting apoptosis

ALA/LA ameliorates glucose toxicity on HK-2 cells by attenuating oxidative stress and apoptosis through the ROS/p38/TGF-β1 pathway

Abstract Background Growing evidence indicates that oxidative stress (OS) plays a pivotal role in Diabetic nephropathy (DN). In a previous study we demonstrated that ALA/LA protected HK-2 cells against high glucose-induced cytotoxicity. So we aimed to establish the glucose injury model of HK-2 cells and investigate the beneficial effects of ALA/LA on high glucose-induced excessive production of TGF-β1 and the possible mechanisms mediating the effects. Methods The expression of OS markers in high glucose-induced HK-2 cells treated with ALA/LA., including the antioxidant enzymes and reactive oxygen species (ROS) production, as well as the apoptosis rate were assayed by ELISA and flow cytometry. The p38/transforming growth factor β1 (TGF-β1) signal pathway were measured by real-time RT-PCR and western blot. Results The modeling condition of glucose toxicity on HK-2 cells was at the glucose concentration of 40.9 mM. ALA/LA can significantly increase the activities of antioxidant enzymes and decrease ROS production stimulated by high glucose. The study also found that ALA/LA caused a decrease in the apoptosis rate and TGF-β1 level of HK-2 cells under high glucose stress through the ROS/p38 pathway. Conclusions ALA/LA exerts protective effects in vitro through inhibition of ROS generation, down regulation of the activation of the p38MAPK pathway and the expression of TGF-β1 in HK-2 cells

Fast switching optical modulator based on dual frequency nematic cell,”

We demonstrate a fast optical modulator capable of switching large amount of optical retardation (a few microns) in less than 1 ms. The result is achieved by employing a dual frequency nematic in cells with high pre-tilt alignment and by providing a special addressing scheme that features amplitude and frequency modulated voltage. We explore the effect of surface alignment and dielectric heating on the switching time. We also report the measurements of dielectric permittivities and crossover frequency of dual frequency nematic

Microstructure and Corrosion Behavior of Laser-Cladding CeO2-Doped Ni-Based Composite Coatings on TC4

Laser-cladding CeO2-doped Ni-based composite coatings were prepared on the surface of a titanium alloy, and the effects of CeO2 addition on the microstructure, microhardness, and corrosion resistance of the prepared coatings were studied. The results showed that TiC, NiTi, Ni3Ti, and Ti2Ni phases were formed on the prepared coatings. Moreover, the addition of CeO2 in laser-cladding coatings effectively refined the microstructure and reduced the number of cracks generated in the laser-cladding process. When the amount of CeO2 was 2%, the number of cracks in the laser-cladding coating was significantly reduced compared with that of 0%. When the content of CeO2 was 2% or 3%, the microhardness of laser-cladding coatings reached the maximum value. At the same time, it was found that the appropriate addition of CeO2 was helpful to improve the corrosion resistance of the laser-cladding coating. However, excessive CeO2 addition could reduce the corrosion resistance of the laser-cladding coating