On some classes of projectively flat Finsler metrics with constant flag curvature

Abstract(#br)In this paper, we give the equivalent PDEs for projectively flat Finsler metrics with constant flag curvature defined by a Euclidean metric and two 1-forms. Furthermore, we construct some classes of new projectively flat Finsler metrics with constant flag curvature by solving these equivalent PDEs

Understory species composition mediates soil greenhouse gas fluxes by affecting bacterial community diversity in boreal forests

IntroductionPlant species composition in forest ecosystems can alter soil greenhouse gas (GHG) budgets by affecting soil properties and microbial communities. However, little attention has been paid to the forest types characterized by understory vegetation, especially in boreal forests where understory species contribute significantly to carbon and nitrogen cycling.MethodIn the present study, soil GHG fluxes, soil properties and bacterial community, and soil environmental conditions were investigated among three types of larch forest [Rhododendron simsii-Larix gmelinii forest (RL), Ledum palustre-Larix gmelinii forest (LL), and Sphagnum-Bryum-Ledum palustre-Larix gmelinii forest (SLL)] in the typical boreal region of northeast China to explore whether the forest types characterized by different understory species can affect soil GHG fluxes.ResultsThe results showed that differences in understory species significantly affected soil GHG fluxes, properties, and bacterial composition among types of larch forest. Soil CO2 and N2O fluxes were significantly higher in LL (347.12 mg m−2 h−1 and 20.71 μg m−2 h−1) and RL (335.54 mg m−2 h−1 and 20.73 μg m−2 h−1) than that in SLL (295.58 mg m−2 h−1 and 17.65 μg m−2 h−1), while lower soil CH4 uptake (−21.07 μg m−2 h−1) were found in SLL than in RL (−35.21 μg m−2 h−1) and LL (−35.85 μg m−2 h−1). No significant differences between LL and RL were found in soil CO2, CH4, and N2O fluxes. Soil bacterial composition was mainly dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Chloroflexi among the three types of larch forest, while their abundances differed significantly. Soil environmental variables, soil properties, bacterial composition, and their interactions significantly affected the variations in GHG fluxes with understory species. Specifically, structural equation modeling suggested that soil bacterial composition and temperature had direct close links with variations in soil GHG fluxes among types of larch forest. Moreover, soil NO3−−N and NH4+ − N content also affected soil CO2, CH4, and N2O fluxes indirectly, via their effects on soil bacterial composition.DiscussionOur study highlights the importance of understory species in regulating soil GHG fluxes in boreal forests, which furthers our understanding of the role of boreal forests in sustainable development and climate change mitigation

Activation of Thromboxane A2 Receptor (TP) Increases the Expression of Monocyte Chemoattractant Protein -1 (MCP-1)/Chemokine (C-C motif) Ligand 2 (CCL2) and Recruits Macrophages to Promote Invasion of Lung Cancer Cells

Thromboxane synthase (TXAS) and thromboxane A2 receptor (TP), two critical components for thromboxane A2 (TXA2) signaling, have been suggested to be involved in cancer invasion and metastasis. However, the mechanisms by which TXA2 promotes these processes are still unclear. Here we show that TXA2 mimetic, I-BOP, induced monocyte chemoattractant protein -1(MCP-1)/chemokine (C-C motif) ligand 2 (CCL2) expression at both mRNA and protein levels in human lung adenocarcinoma A549 cells stably over-expressing TP receptor α isoform (A549-TPα). The induction of MCP-1 was also found in other lung cancer cells H157 and H460 that express relatively high levels of endogenous TP. Using specific inhibitors of several signaling molecules and promoter/luciferase assay, we identified that transcription factor SP1 mediates I-BOP-induced MCP-1 expression. Furthermore, supernatants from I-BOP-treated A549-TPα cells enhanced MCP-1-dependent migration of RAW 264.7 macrophages. Moreover, co-culture of A549 cells with RAW 264.7 macrophages induced expression of MMPs, VEGF and MCP-1 genes, and increased the invasive potential in A549 cells. These findings suggest that TXA2 may stimulate invasion of cancer cells through MCP-1-mediated macrophage recruitment