SMA observations of C2H in High-Mass Star Forming Regions

C$_2$H is a representative hydrocarbon that is abundant and ubiquitous in the interstellar medium (ISM). To study its chemical properties, we present Submillimeter Array (SMA) observations of the C$_2$H $N=3-2$ and HC$_3$N $J=30-29$ transitions and the 1.1 mm continuum emission toward four OB cluster-forming regions, AFGL 490, ON 1, W33 Main, and G10.6-0.4, which cover a bolometric luminosity range of $\sim$10$^3$--10$^6$ $L_{\odot}$. We found that on large scales, the C$_2$H emission traces the dense molecular envelope. However, for all observed sources, the peaks of C$_2$H emission are offset by several times times 10$^4$ AU from the peaks of 1.1 mm continuum emission, where the most luminous stars are located. By comparing the distribution and profiles of C$_2$H hyperfine lines and the 1.1 mm continuum emission, we find that the C$_2$H column density (and abundance) around the 1.1 mm continuum peaks is lower than those in the ambient gas envelope. Chemical models suggest that C$_2$H might be transformed to other species owing to increased temperature and density; thus, its reduced abundance could be the signpost of the heated molecular gas in the $\sim$10$^4$ AU vicinity around the embedded high-mass stars. Our results support such theoretical prediction for centrally embedded $\sim10^3$--$10^6L_{\odot}$ OB star-forming cores, while future higher-resolution observations are required to examine the C$_2$H transformation around the localized sites of high-mass star formation.Comment: 10 pages, 6 figures. ApJ accepted. Comments welcom

Adjusting the structure combinations of plant communities in urban greenspace reduced the maintenance energy consumption and GHG emissions

Maintaining urban greenspace results in energy use and GHG emissions. To understand the change of the annual maintenance energy consumption and GHG emissions in varying combinations of plant structures (plant density or proportion of area covered) in urban greenspace, this study investigated 34 urban plant communities as sample plots (20×20 m), and divided them into woodland, shrub, herbaceous and grassland layers. The average energy use and GHG emissions in the woodland layer were 18.64 MJ/tree/y–1 and 0.23 kg/CO2-e/tree/y–1, respectively. In the shrub, herbaceous, and grassland layers, the average energy consumption was 3.73, 2.27, 7.23 MJ/m2/y–1, and the average GHG emissions were 0.06, 0.02, 0.09 kg/CO2-e/m2/y–1, respectively. The energy use and GHG emission curves had parabolic trends as the plant density in the woodland layer increased and increasing curves with two peaks as the plant area proportions of the shrub, herbaceous, and grassland layers increased. The annual maintenance of urban greenspace can divide into low, average and high levels of energy consumption and GHG emissions due to the change in the plant structure combinations. Furthermore, city managers and landscape designers can refer to the energy consumption and GHG emissions trends to understand the environmental impact of maintenance tasks. The future plant structures in greenspace can be better designed to improve ecosystem services based on limiting the maintenance environmental impacts

Merger-induced star formation in low-metallicity dwarf galaxy NGC 4809/4810

The physical mechanisms driving starbursts in dwarf galaxies are unclear, and the effects of mergers on star formation in these galaxies are still uncertain. We explore how the merger process affects star formation in metal-poor dwarf galaxies by analyzing high-spatial-resolution ($\sim$ 70 pc) integral field spectrograph observations of ionized gas. We use archival data from the Very Large Telescope/Multi Unit Spectroscopic Explorer to map the spatial distribution of strong emission lines (e.g., $\rm H\beta$, $\rm H\alpha$, $\rm [OIII]\lambda5007$, $\rm [NII]\lambda6583$, etc) in the nearby merging star-forming dwarf galaxy system NGC 4809/4810. We identify approximately 112 star-forming knots scattered among the two galaxies, where the gas-phase metallicity distribution is inhomogeneous and mixing with metal-poor and metal-rich ionized gas. Star-forming knots at the interacting region show lower metallicity, the highest star formation rates (SFRs) and SFR to resolved main-sequence-relation (rMSR) ratios. Ionized gas exhibits an obvious northeast-southwest velocity gradient in NGC 4809, while seemingly mixed in NGC 4810. High virial parameters and the stellar mass-size relation of HII regions indicate that these regions are dominated by direct radiation pressure from massive stars/clusters and persistently expanding. We find two different stellar mass surface density-stellar age relations in NGC 4809 and NGC 4810, and the stellar ages of NGC 4810 are systematically younger than in NGC 4809. Our study suggests that the merging stage of two dwarf galaxies can induce starburst activities at the interaction areas, despite the metal-deficient environment. Considering the high specific SFRs and different stellar ages, we propose that the interaction initially triggered star formation in NGC 4809 and then drove star formation in NGC 4810.Comment: 13 pages, 12 figures; accepted for publication in A&

Astragalin Promotes Osteoblastic Differentiation in MC3T3-E1 Cells and Bone Formation in vivo

Astragalin (AG) is a biologically active flavonoid compound that can be extracted from a number of medicinal plants. However, the effects of AG on osteoblastic differentiation in mouse MC3T3-E1 cells and on bone formation in vivo have not been studied fully. In this study, we found that the activities of alkaline phosphatase (ALP) and mineralized nodules in MC3T3-E1 cells were both significantly increased after treatment with AG (5, 10, and 20 μM). Meanwhile, the mRNA and protein levels of osteoblastic marker genes in MC3T3-E1 cells after AG treatment were markedly increased compared with a control group. In addition, the levels of BMP-2, p-Smad1/5/9, and Runx2 were significantly elevated in AG-treated MC3T3-E1 cells. Moreover, we found that the protein levels of Erk1/2, p-Erk1/2, p38, p-p38, and p-JNK were also significantly increased in AG-treated MC3T3-E1 cells compared to those in the control group. Finally, in vivo experiments demonstrated that AG significantly promoted bone formation in an ovariectomized (OVX)-induced osteoporotic mouse model. This was evidenced by significant increases in the values of osteoblast-related parameters (BFR/BS, MAR, Ob.S/BS, and Ob.N/B.Pm) and bone histomorphometric parameters (BMD, BV/TV, Tb.Th, and Tb.N.) in OVX mice after AG treatment (5, 10, and 20 mg/kg). Collectively, these results demonstrated that AG may promote osteoblastic differentiation in MC3T3-E1 cells via the activation of the BMP and MAPK pathways and promote bone formation in vivo. These novel findings indicated that AG may be a useful bone anabolic agent for the prevention and treatment of osteoporosis