The optimization of SO2 emissions by the 4DVAR and EnKF methods and its application in WRF-Chem.

Emissions are essential for forecasting air quality and pollution control, but traditional emissions are often not real-time by the statistics of "bottom-up" approach due to high human resource demand. The four-dimensional variational method (4DVAR) and the ensemble Kalman filter (EnKF) are generally used to optimize emissions based on chemical transport models by assimilating observations. Although the two methods solve similar estimation problems, different functions have been developed to address the process of converting the emissions to concentrations. In this paper, we evaluated the performance of the 4DVAR and EnKF methods in optimizing SO2 emissions over China during 23-29 January 2020. The emissions optimized by the 4DVAR and EnKF methods showed a similar spatiotemporal distribution in most regions of China during the study period, suggesting that both methods are useful in reducing uncertainties in the prior emissions. Three forecast experiments with different emissions were conducted. Compared with the forecasts with prior emissions, the root-mean-square error of the forecasts with the emissions optimized by the 4DVAR and EnKF methods decreased by 45.7 % and 40.4 %. This indicates that the 4DVAR method was slightly more effective than the EnKF method in optimizing emissions and improves the accuracy of forecasts. Furthermore, it is found that the 4DVAR method performed better than the EnKF method when the spatial and/or temporal distribution of SO2 observations with strong local characteristics, The EnKF method showed a better performance for the condition of the large difference between prior emissions and real emissions. The results may help to design suitable assimilation algorithms for optimizing emissions and improving model forecasts. The advance data assimilation systems are beneficial for the understanding the effectiveness and value of emission inventories and air quality model.

Multi-scale three-dimensional variational data assimilation for high-resolution aerosol observations: Methodology and application.

With an increasing number of air quality monitoring stations installed around the Chinese mainland, high-resolution aerosol observations become available, allowing improvements in air pollution monitoring and aerosol forecasting. However, the multi scales (especially small-scale) information included in high-resolution aerosol observations could not be effectively utilized by the traditional three-dimensional variational method (3DVAR). This study attempted to extend the traditional 3DVAR to a multi-scale 3DVAR with two iteration steps, two-scale-3DVAR (TS-3DVAR), to improve the effectiveness of assimilating high-resolution observations. In TS-3DVAR, the large-scale and small-scale components of observation information were decomposed from the original high-resolution observations using a Gaussian smoothing method and then assimilated using the corresponding large-scale or small-scale background error covariances which were derived from the partitioned background error samples. The data assimilation (DA) analysis field generated by TS-3DVAR is more accurate than 3DVAR in reproducing the field's multi-scale characteristics, which could thus be used as the initial chemical field of the air quality model to improve aerosol forecasting. Particulate matter with an aerodynamic diameter of less than 2.5 µm (PM2.5) and 10.0 µm (PM10) from the surface air quality monitoring stations from November 01 to November 30, 2018 at 00:00 were assimilated daily to verify the effects of TS-3DVAR and 3DVAR on the aerosol analysis and forecast accuracy. The results showed that TS-3DVAR better constrained both large-scale and small-scale, especially the spatial wavelengths in a range of 54-216 km and those above 351 km. The average power spectra of the TS-3DVAR assimilation increment in the two wavelength ranges were 71.70% and 35.33% higher than those of 3DVAR. As a result, the TS-3DVAR was more effective than 3DVAR in improving the accuracy of the initial chemical field, and thereby the forecasting capability for PM2.5. In the initial chemical field, the 30-day average correlation coefficient (Corr) of PM2.5 of TS-3DVAR was 0.052 (6.12%) higher than that of 3DVAR, and the root mean square error (RMSE) of TS-3DVAR was 3.446 µg m-3 (16.4%) lower than that of 3DVAR. For the forecasting capability for PM2.5 mass concentration, the 30-day average Corr of TS-3DVAR during the 0-24 hour forecast period was 0.025 (5.08%) higher than that of 3DVAR, and the average RMSE was 2.027 µg m-3 (4.85%) lower. The positive effect of TS-3DVAR on the improvement of forecasting capability can last for more than 24 h.

Circular RNA Circ_0013958 Functions as a Tumor Promoter in Ovarian Cancer by Regulating miR-637/PLXNB2 Axis.

Background: Circular RNAs (circRNAs) have emerged as important regulators in diverse human malignancies, including ovarian cancer (OC). This study was performed to explore the function and regulatory mechanism underlying circ_0013958 in OC progression. Methods: Quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot assay was applied to examine the expression of circ_0013958, microRNA-637 (miR-637), and Plexin B2 (PLXNB2). The target relationship between miR-637 and circ_0013958 or PLXNB2 was verified by dual-luciferase reporter assay or RNA immunoprecipitation (RIP) assay. Cell Counting Kit-8 (CCK-8) and colony formation assays were employed to detect cell viability and clonogenicity ability, respectively. Cell migration and invasion were analyzed by Transwell assay. Cell apoptosis was monitored by flow cytometry. The role of circ_0013958 in vivo was determined by xenograft tumor assay. Results: Circ_0013958 and PLXNB2 were upregulated, while miR-637 was downregulated in OC tissues and cells. Circ_0013958 acted as a sponge for miR-637 to regulate the expression of PLXNB2 in OC cells. The repression effects of circ_0013958 knockdown on cell proliferation, migration, invasion, and apoptosis in OC cells were partly attenuated by the miR-637 inhibitor. And miR-637 targeted PLXNB2 to suppress OC cell proliferation, migration, and invasion. Moreover, circ_0013958 silencing blocked OC tumor growth in vivo. Conclusion: Circ_0013958 knockdown impeded OC development through modulating the miR-637/PLXNB2 axis, highlighting a therapeutic target for OC.

The chemical mechanisms of the enzymes in the branched-chain amino acids biosynthetic pathway and their applications.

l-Valine, l-isoleucine, and l-leucine are three key proteinogenic amino acids, and they are also the essential amino acids required for mammalian growth, possessing important and to some extent, special physiological and biological functions. Because of the branched structures in their carbon chains, they are also named as branched-chain amino acids (BCAAs). This review will highlight the advance in studies of the enzymes involved in the biosynthetic pathway of BCAAs, concentrating on their chemical mechanisms and applications in screening herbicides and antibacterial agents. The uses of some of these enzymes in lab scale organic synthesis are also discussed.

Preparation of a whole cell catalyst overexpressing acetohydroxyacid synthase of Thermotoga maritima and its application in the syntheses of α-hydroxyketones.

The large catalytic subunit of acetohydroxyacid synthase (AHAS, EC 2.2.1.6) of Thermotoga maritima (TmcAHAS) was prepared in this study. It possesses high specific activity and excellent stability. The protein and a whole cell catalyst overexpressing the protein were applied to the preparation of α-hydroxyketones including acetoin (AC), 3-hydroxy-2-pentanone (HP), and (R)-phenylacetylcarbinol (R-PAC). The results show that AC and HP could be produced in high yields (84% and 62%, respectively), while R-PAC could be synthesized in a high yield (about 78%) with an R/S ratio of 9:1. Therefore, TmcAHAS and the whole cell catalyst overexpressing the protein could be practically useful bio-catalysts in the preparation of α-hydroxyketones including AC, HP, and R-PAC. To the best of our knowledge, this is the first time that bacterial AHAS was used as a catalyst to prepare HP with a good yield, and also the first time that TmcAHAS was employed to synthesize AC and R-PAC.

CCCH-type zinc finger antiviral protein mediates antiviral immune response by activating T cells.

The zinc finger antiviral protein (ZAP), as a host restriction factor, inhibits the replication of certain viruses by binding viral mRNA or proteins for degradation. However, little is known about the role of ZAP in the antiviral immune response. We now show that ZAP participates in the antiviral immune response by activating T cells. Overexpression of ZAP significantly inhibited avian leukosis virus subgroup J (ALV-J) replication and reduced the associated inflammatory damage in vivo. In this study, we found that ZAP tended to be expressed in T lymphocytes, especially after ALV-J infection. T lymphocyte proliferation proceeded as usual in response to ALV-J infection in the presence of ZAP, indicating that ZAP endows T lymphocytes with resistance to the immunosuppression caused by ALV-J. Furthermore, ZAP activated cytokine secretion by T lymphocytes by contributing to nuclear translocation of nuclear factors of activated T cells and indirectly promoted anti-ALV-J antibody generation. Together, our findings show that ZAP, acting as an immunomodulatory factor, is involved in the antiviral immune response via T lymphocyte activation.

Stability and stabilization of (-)-gallocatechin gallate under various experimental conditions and analyses of its epimerization, auto-oxidation, and degradation by LC-MS.

BACKGROUND: (-)-Gallocatechin gallate (GCG) shows multi-bioactivities. Its stability, however, has not been investigated systematically yet. Therefore, the objective of this study was to characterize the stability of GCG and to find ways to stabilize it in biological assays. Furthermore, the epimerization of the compound, its auto-oxidation and degradation were also analyzed by liquid chromatography mass spectrometry (LC-MS). RESULTS: The stability of GCG was concentration-dependent and was sensitive to pH, temperature, bivalent cations, and dissolved oxygen level. The results also showed that GCG was not stable in common buffers (50 mmol L-1 , pH 7.4, 37 °C) or in cell culture medium DMEM/F12 under physiological conditions (pH 7.4, 37 °C). Our experiments indicated that nitrogen-saturation and the addition of ascorbic acid (VC) could stabilize GCG in biological assays. In addition, LC-MS determination indicated that GCG was able to be epimerized to its epimer (-)-epigallocatechin gallate (EGCG). Meanwhile it was also able to be auto-oxidized to theasinensin and compound P2 and degraded to gallocatechin and gallic acid in pure water at 100 °C. CONCLUSION: The stability of GCG should be seriously considered in research on the bioactivity of it to avoid possible artifacts. Nitrogen-saturation and use of VC are good ways to make GCG stable in biological assays. © 2019 Society of Chemical Industry.

Determination of the Activity of 1-Deoxy-D-Xylulose 5-Phosphate Synthase by Pre-column Derivatization-HPLC Using 1,2-Diamino-4,5-Methylenedioxybenzene as a Derivatizing Reagent.

α-Ketoacids can be determined by HPLC through pre-column derivatization with 1,2-diamino-4,5-methylenedioxybenzene (DMB) as a derivatizing reagent. Using this method, the specific activity and the steady-state kinetic of 1-deoxy-D-xylulose-5-phosphate synthase (DXS) were measured. Firstly, DXS substrate pyruvate was derivatized with DMB in acidic solution; then the corresponding quinoxalinone was elucidated by LC-ESI-MS and quantified by HPLC-UV. The optimum derivatization conditions were as follows: aqueous medium at pH 1.0, reaction temperature 80 °C, reaction time 60 min, molar ratio of DMB to pyruvate 10:1. The HPLC was run with isocratic elution using the mixture of methanol and water (60:40, v/v) as a mobile phase. The detective limit and the linear correlation range of the method were 0.05 µM and 0.002-1.0 mM (R = 0.994), respectively. The relative standard deviation (RSD) of six determinations was 2.48%. The steady-state kinetic parameters of DXS for pyruvate determined with the method were identical to the reported data. The established method is a practical route for evaluation of DXS activity, especially in the research and development of DXS inhibitors.

A Newly Designed Composite Gel Polymer Electrolyte Based on Poly(Vinylidene Fluoride-Hexafluoropropylene) (PVDF-HFP) for Enhanced Solid-State Lithium-Sulfur Batteries.

Developing high-performance solid-state electrolytes is crucial for the innovation of next-generation lithium-sulfur batteries. Herein, a facile method for preparation of a novel gel polymer electrolyte (GPE) based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) is reported. Furthermore, Li1.5 Al0.5 Ti1.5 (PO4 )3 (LATP) nanoparticles as the active fillers are uniformly embedded into the GPE to form the final PVDF-HFP/LATP composite gel polymer electrolyte (CPE). Impressively, the obtained CPE demonstrates a high lithium ion transference number of 0.51 and improved electrochemical stability as compared to commercial liquid electrolyte. In addition, the assembled solid-sate Li-S battery with the composite gel polymer electrolyte membrane presents a high initial capacity of 918 mAh g-1 at 0.05 C, and better cycle performance than the counterparts with liquid electrolyte. Our designed PVDF-HFP/LATP composite can be a promising electrolyte for next-generation solid-state batteries with high cycling stability.

A third polymorph of 1,4-bis-(1H-benzimid-azol-2-yl)benzene.

The title compound, C20H14N4, is a new polymorph of the previously reported structures, which were ortho-rhom-bic, space group Pbca [Bei et al. (2000). Acta Cryst. C56, 718-719] and monoclinic, space group P21/c [Dudd et al. (2003). Green Chem. 5, 187-192]. The asymmetric unit consists of two independent mol-ecules in which the dihedral angels between the central benzene ring and the outer benzimidazole ring systems are 16.81 (10) and 14.23 (10)° in one molecule and 26.09 (10) and 37.29 (10)° in the other. In the crystal, mol-ecules are linked by N-H⋯N and C-H⋯N hydrogen bonds into a tape running along the c-axis direction.