Effect of ecological restoration programs on dust concentrations in the North China Plain: a case study

In recent decades, the Chinese government has made a great effort in initiating large-scale ecological restoration programs (ERPs) to reduce the dust concentrations in China, especially for dust storm episodes. Using the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover product, the ERP-induced land cover changes are quantitatively evaluated in this study. Two obvious vegetation protective barriers arise throughout China from the southwest to the northeast, which are well known as the "Green Great Wall" (GGW). Both the grass GGW and forest GGW are located between the dust source region (DSR) and the densely populated North China Plain (NCP). To assess the effect of ERPs on dust concentrations, a regional transport/dust model (WRF-DUST, Weather Research and Forecast model with dust) is applied to investigate the evolution of dust plumes during a strong dust storm episode from 2 to 8 March 2016. The WRF-DUST model generally performs reasonably well in reproducing the temporal variations and spatial distributions of near-surface [PMC] (mass concentration of particulate matter with aerodynamic diameter between 2.5 and 10 mu m) during the dust storm event. Sensitivity experiments have indicated that the ERP-induced GGWs help to reduce the dust concentration in the NCP, especially in BTH (Beijing, Tianjin, and Hebei). When the dust storm is transported from the upwind DSR to the downwind NCP, the [PMC] reduction ranges from -5 to -15% in the NCP, with a maximum reduction of -12.4% (-19.2 mu gm(3)) in BTH and -7.6% (-10.1 mu g m(3)) in the NCP. We find the dust plumes move up to the upper atmosphere and are transported from the upwind DSR to the downwind NCP, accompanied by dust decrease. During the episode, the forest GGW is nonsignificant in dust concentration control because it is of benefit for dry deposition and not for emission. Conversely, the grass GGW is beneficial in controlling dust erosion and is the dominant reason for [PMC] decrease in the NCP. Because the air pollution is severe in eastern China, especially in the NCP, and the contribution of dust episodes is significant, the reduction of dust concentrations will have important effects on severe air pollution. This study illustrates the considerable contribution of ERPs to the control of air pollution in China, especially in springtime

Demethylation of 5,n-di-tert-butyl-8,n-dimethoxy[2.n] metacyclophane-1-ynes with BBr3 to afford novel [n] benzofuranophanes

© 2016 Elsevier B.V. All rights reserved. Novel [n]benzofuranophanes (n = 8 & 10) 2a-b have been prepared by successive intramolecular cyclization from 5,19-di-tert-butyl-8,22-dimethoxy[n]metacyclophane-1-yne (syn-1a-b) by treatment with BBr 3 in CH 2 Cl 2 at room temperature for 8h. [2.n]Benzofuranophanes 2a-b were also obtained by treatment of 1,2-di-endo-bromo-5,19-di-tert-butyl-8,22-dimethoxy[n] metacyclophane (meso-3a-b) with BBr 3 in CH 2 Cl 2 by using the same reaction conditions. 1 H NMR spectra of 2a-b reveals the formation of intramolecular hydrogen bonding between hydroxyl proton with the oxygen of the furan moiety and X-ray analysis shows that the lengths between H (OH) and O (furan) are 1.981 and 1.823 Å, respectively. The conformation of [8]benzofuranophane 2a in solution is rigid with restricted rotation around the diaryl linkage rather than [10] benzofuranophane 2b because of weak intramolecular hydrogen bonding and the short length of the cross-linking chain

Synthesis, structures and Lewis‐Acid‐Induced isomerization of 8‐Methoxy[2.2]metaparacyclophanes and a DFT study

Methyl substituted 8‐methoxy[2.2]MPCPs 8 a–b were obtained via thiacyclophane and its oxidized products. Lewis acid‐catalyzed (AlCl3‐MeNO2) reactions of 5‐tert‐butyl‐8‐methoxy‐12,13,15,16‐tetramethyl[2.2]MPCP 8 b under various conditions led to transannular cyclization and isomerization reactions, affording the considerably less‐strained 5‐tert‐butyl‐8‐methoxy[2.2]MPCP 9, 5‐tert‐butyl‐8‐hydroxy‐14,16,17,18‐tetramethyl[2.2]metacyclophane 10 and pyrene derivatives 11 and 12. However,on prolonging the reaction time to 3 h for 8 b, the major product is 5‐tert‐butyl‐8‐hydroxy[2.2]MPCP 10. These reactions are strongly affected by the size and properties of the C‐8 substitutents as well as the methyl substitutents on the para‐linked benzene rings, which increase the strain in the molecules. The 1H NMR spectra and X‐ray crystallographic analysis of 8 b revealed that it adopts a syn‐conformation both in solution and in the solid state

Anti‐inflammatory effects and molecular mechanisms of 8‐prenyl quercetin

Scope: 8-prenyl quercetin (PQ) is a typical prenylflavonoid distributed in plant foods and shows higher potential bioactivity than its parent quercetin (Q) although the mechanisms are not fully understood. This study aims to clarify the anti-inflammatory effects and molecular mechanisms of PQ in cell and animal models, compared to Q. Methods and results: RAW264.7 cells were treated with PQ or Q to investigate the influence on the production of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and protein kinases by Western blotting. Nitric oxide (NO) and prostaglandin E2 (PGE2) were measured by the Griess method and ELISA, respectively. Cytokines were assayed by the multiplex technology. Mouse paw edema was induced by lipopolysaccharide (LPS). The results revealed that PQ had stronger inhibition on the productions of iNOS, COX-2, NO, PGE2, and 12 kinds of cytokines, than Q. PQ also showed in vivo anti-inflammatory effect by attenuating mouse paw edema. Molecular data revealed that PQ had no competitive binding to Toll-like receptor 4 (TLR4) with LPS, but directly targeted SEK1-JNK1/2 and MEK1-ERK1/2. Conclusion: PQ as a potential inhibitor revealed anti-inflammatory effect in both cell and animal models at least by targeting SEK1-JNK1/2 and MEK1-ERK1/2

Anti‐inflammatory effects and molecular mechanisms of 8‐prenyl quercetin

Scope: 8-prenyl quercetin (PQ) is a typical prenylflavonoid distributed in plant foods and shows higher potential bioactivity than its parent quercetin (Q) although the mechanisms are not fully understood. This study aims to clarify the anti-inflammatory effects and molecular mechanisms of PQ in cell and animal models, compared to Q. Methods and results: RAW264.7 cells were treated with PQ or Q to investigate the influence on the production of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and protein kinases by Western blotting. Nitric oxide (NO) and prostaglandin E2 (PGE2) were measured by the Griess method and ELISA, respectively. Cytokines were assayed by the multiplex technology. Mouse paw edema was induced by lipopolysaccharide (LPS). The results revealed that PQ had stronger inhibition on the productions of iNOS, COX-2, NO, PGE2, and 12 kinds of cytokines, than Q. PQ also showed in vivo anti-inflammatory effect by attenuating mouse paw edema. Molecular data revealed that PQ had no competitive binding to Toll-like receptor 4 (TLR4) with LPS, but directly targeted SEK1-JNK1/2 and MEK1-ERK1/2. Conclusion: PQ as a potential inhibitor revealed anti-inflammatory effect in both cell and animal models at least by targeting SEK1-JNK1/2 and MEK1-ERK1/2

Studies on Lewis-Acid Induced Reactions of 8-Methoxy[2.2]metacyclophanes: A New Synthetic Route to Alkylated Pyrenes

Anti-8-methoxy[2.2]metacyclophanes (MCPs) 5 a–b were obtained via pyrolysis of the corresponding syn-thiatetraoxide cyclophanes 4 a–b. Coupling reactions of 4-tert-butyl-1-methoxy-2,6-bis(mercaptomethyl)benzenes 1 a–b and 1,5-bis(chloro-methyl)-2,4-dimethylbenzene 2 under high dilution conditions afforded only the syn-conformers of 9-methoxy-2,11-dithia[3.3]metacyclophanes 3 a–b, which with m-CPBA formed the corresponding syn-tetraoxides 4 a–b. Lewis acid (TICl4/AlCl3-MeNO2) or iodine-catalyzed reactions of 5 b under various conditions led to transannular cyclization to afford tetrahydropyrene 6 b and pyrene derivative 7 b and/or de-tert-butylated 6 a. Iodine-catalyzed reaction of 5 a afforded tetrahydropyrene 6 a. These findings suggest the potential for a new route to alkylated pyrenes via strained and alkylated metacyclophanes. Density functional theory (DFT) studies were carried out to investigate the conformational characteristics of 3–5