Isolation of Potential Photosynthetic N\u3csub\u3e2\u3c/sub\u3e-Fixing Microbes from Topsoil of Native Grasslands in South Dakota

Nitrogen fertilizer is one of the most limiting factors and costly inputs in agriculture production. Current fossil fuel-dependent ammonia production is both energy intensive and environmentally damaging. An economically practical and environmentally friendly solution for the production of ammonia is urgently needed. Solar-powered N2-fixing cyanobacteria provide a unique opportunity and promise for applications in agriculture compared to all other N2-fixing bacteria that cannot use solar energy. Isolation of nitrogen-fixing microbes from the topsoil of native grasslands may have the potential to use them in crop fields as living ammonia factories. This may be a mechanism to free farmers from heavy reliance on fossil fuels-dependent chemical nitrogen fertilizers and to improve soil health for sustainable agriculture. To screen for solar-powered N2-fixing cyanobacteria in topsoil of native grasslands in South Dakota, we collected 144 topsoil samples from several native grasslands. Six photosynthetic microbial strains were isolated that are capable of growing well autotrophically in a nitrogen-free medium, suggesting that these six microbial strains have the ability to fix N2. They were assigned the names: Xu15, Xu81, Xu86, Xu111, Xu141, and WW3. Based on cell morphology and its 18S rRNA gene sequence that we obtained, strain Xu15 was reassigned as Chloroidium saccharophilum Xu15, a common terrestrial coccoid green alga. An acetylene reduction assay detected substantial ethylene production, suggesting nitrogenase activity occurrences in cultures Xu81 and Xu15. The other four are in the process of purification for testing their nitrogenase activity. Xu81, Xu111 and Xu141 are probably unicellular microalga, while WW3 and Xu86 are likely filamentous cyanobacteria. Future research will focus on developing these validated N2-fixing microbes as in situ living ammonia factories in crop fields

Heat transfer characteristics of a binary thin liquid film in a microchannel with constant heat flux boundary condition

Thin film evaporation of multi-component fluids in microchannels is important in many industrial applications, which requires comprehensive modeling of the transport mechanisms in the liquid, gas and solid phases. This paper presents a numerical study on the heat transfer characteristics of a binary thin liquid film in a micro channel with constant heat flux boundary condition, using the enhanced Young-Laplace equation that considers the effect of disjoining pressure for binary fluids. Effects of temperature, microchannel size, and non-condensable gas on the binary thin film heat transfer was analyzed. The results show that the thin film contribution to the total heat transfer rate reduces when the initial temperature increases, but the difference between them decreases as the microchannel size reduces. Size effect can be prominent when the characteristic microchannel size is smaller than 10 gm. When the microchannel size decreases, the cumulative heat transfer rate across the interface of the solution decreases, while the thin film contribution to the total heat transfer rate increases obviously. The non-condensable gas deteriorates the cumulative heat transfer rate, but the deterioration reduces under the high temperature condition as compared to that under the low temperature condition. Comparison of the results shows that the temperature and microchannel size have the greatest effect on the heat transfer followed by the non-condensable gas. This can be efficiently utilized for heat transfer enhancement and thermal design in applications involving phase-change heat transfer of multi-component fluids in microchannels

Reduced CTGF expression promotes cell growth, migration, and invasion in nasopharyngeal carcinoma.

BACKGROUND:The role of CTGF varies in different types of cancer. The purpose of this study is to investigate the involvement of CTGF in tumor progression and prognosis of human nasopharyngeal carcinoma (NPC). EXPERIMENTAL DESIGN:CTGF expression levels were examined in NPC tissues and cells, nasopharynx (NP) tissues, and NP69 cells. The effects and molecular mechanisms of CTGF expression on cell proliferation, migration, invasion, and cell cycle were also explored. RESULTS:NPC cells exhibited decreased mRNA expression of CTGF compared to immortalized human nasopharyngeal epithelial cell line NP69. Similarly, CTGF was observed to be downregulated in NPC compared to normal tissues at mRNA and protein levels. Furthermore, reduced CTGF was negatively associated with the progression of NPC. Knocking down CTGF expression enhanced the colony formation, cell migration, invasion, and G1/S cell cycle transition. Mechanistic analysis revealed that CTGF suppression activated FAK/PI3K/AKT and its downstream signals regulating the cell cycle, epithelial-mesenchymal transition (EMT) and MMPs. Finally, DNA methylation microarray revealed a lack of hypermethylation at the CTGF promoter, suggesting other mechanisms are associated with suppression of CTGF in NPC. CONCLUSION:Our study demonstrates that reduced expression of CTGF promoted cell proliferation, migration, invasion and cell cycle progression through FAK/PI3K/AKT, EMT and MMP pathways in NPC