Modeling Studies of Gravity Wave Dynamics in Highly Structured Environments: Reflection, Trapping, Instability, Momentum Transport, Secondary Gravity Waves, and Induced Flow Responses

A compressible numerical model is applied for three-dimensional (3-D) gravity wave (GW) packets undergoing momentum deposition, self-acceleration (SA), breaking, and secondary GW (SGW) generation in the presence of highly-structured environments enabling thermal and/or Doppler ducts, such as a mesospheric inversion layer (MIL), tidal wind (TW), or combination of MIL and TW. Simulations reveal that ducts can strongly modulate GW dynamics. Responses modeled here include reflection, trapping, suppressed transmission, strong local instabilities, reduced SGW generations, higher altitude SGW responses, and induced large-scale flows. Instabilities that arise in ducts experience strong dissipation after they emerge, while trapped smaller-amplitude and smaller-scale GWs can survive in ducts to much later times. Additionally, GW breaking and its associated dynamics enhance the local wind along the GW propagation direction in the ducts, and yield layering in the wind field. However, these dynamics do not yield significant heat transport in the ducts. The failure of GW breaking to induce stratified layers in the temperature field suggests that such heat transport might not be as strong as previously assumed or inferred from observations and theoretical assessments. The present numerical simulations confirm previous finding that MIL generation may not be caused by the breaking of a transient high-frequency GW packet alone

Suppressed N fixation and diazotrophs after four decades of fertilization

Background: N fixation is one of the most important microbially driven ecosystem processes on Earth, allowing N to enter the soil from the atmosphere, and regulating plant productivity. A question that remains to be answered is whether such a fundamental process would still be that important in an over-fertilized world, as the long-term effects of fertilization on N fixation and associated diazotrophic communities remain to be tested. Here, we used a 35-year fertilization experiment, and investigated the changes in N fixation rates and the diazotrophic community in response to long-term inorganic and organic fertilization. Results: It was found that N fixation was drastically reduced (dropped by 50%) after almost four decades of fertilization. Our results further indicated that functionality losses were associated with reductions in the relative abundance of keystone and phylogenetically clustered N fixers such as Geobacter spp. Conclusions: Our work suggests that long-term fertilization might have selected against N fixation and specific groups of N fixers. Our study provides solid evidence that N fixation and certain groups of diazotrophic taxa will be largely suppressed in a more and more fertilized world, with implications for soil biodiversity and ecosystem functions

Oxygen-Glucose Deprivation Induced Glial Scar-Like Change in Astrocytes

It has been demonstrated that cerebral ischemia induces astrocyte reactivity, and subsequent glial scar formation inhibits axonal regeneration during the recovery phase. Investigating the mechanism of glial scar formation will facilitate the development of strategies to improve axonal regeneration. However, an in vitro model of ischemia-induced glial scar has not yet been systematically established.In the present study, we at the first time found that oxygen-glucose deprivation (OGD) in vitro can induce rat cortical astrocytes to present characteristics of glial scar. After OGD for 6 h, astrocytes showed a remarkable proliferation following 24 h reperfusion, evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and BrdU immunocytochemistry. Meanwhile, the expression of glial fibrillary acidic protein significantly increased, so did the expression of neurocan, which is a hallmark of the glial scar. In further experiments, neurons were co-cultured with astrocytes, which had been exposed to OGD, and then the immunostaining of class III β-tubulin was carried out to assess the neurite growth. When the co-culture was performed at 48 h reperfusion of astrocytes, the neurite growth was obviously inhibited, and this inhibition could be reversed by chondroitinase ABC, which digests glycosaminoglycan chains on CSPGs, including neurocan. However, the processes of neurons were elongated, when the co-culture was performed immediately after OGD.Our results indicated that after conditioned OGD the astrocytes presented the characteristics of the glial scar, which are also comparable to the astrocytes in acute and chronic phases after cerebral ischemia in vivo. Therefore, the present system may be used as an in vitro model to explore the mechanisms underlying glial scar formation and the treatments to improve axonal regeneration after cerebral ischemia

The Application of LM-BP Neural Network in the Prediction of Total Output Value of Agriculture

Gross agricultural product is an important indication to measure the agricultural development level of a region. It would be affected by many factors, having the characteristics of non-linearity. For this reason, LM-BP neural network was put forward as the model and method for predicting gross agricultural product. Taking the indications of the sown area of crop, the output of grain, sugarcane, cassava, tea, meat, aquatic products, turpentine and oil-tea camellia seed, etc. as inputs, during 2000 to 2012 in Guangxi, the gross agricultural product data from the analysis of simulation experiment show that the prediction of LM-BP neural network fits well with actual results

PGC-1α is associated with Schizothorax prenanti myoblast differentiation

PGC-1α has been considered as an important mediator of functional capacity of muscle. Our previous study indicated that the mRNA level of PGC-1α increased in muscle during Schizothorax prenanti (S. prenanti) growth. To understand the biological significance of PGC-1α up-regulation, S. prenanti myosatellite cells were isolated and the function of PGC-1α in myoblast differentiation was further investigated. The results indicated that PGC-1α over-expressing transfectants fused to form myotubes with higher mRNA level of myosin heavy chain isoform I (MyHCI). No obvious differentiation was observed in PGC-1α-targeted shRNA-transfected cells with a marked decrement of MyHCI expression. Furthermore, S. prenanti PGC-1α increased the expression of MyoD and MyoG, which controlled the commitment of precursor cells to myotubes. In contrast, the levels of MyoD and MyoG mRNA were down-regulated with shRNA-targeting PGC-1α transfection. These investigations indicate that PGC-1α is associated with myoblast differentiation and it elevates MyoD and MyoG expression levels in S. prenanti myoblast cells

Synthesis and Evaluation of Bio-Based Plasticizers from 5-Hydroxymethyl-2-Furancarboxylic Acid for Poly(vinyl chloride)

5-Hydroxymethyl-2-furancarboxylic acid (HFCA), a promising biomonomer from renewable resources, was used to synthesize two bio-based plasticizers, namely, hexyl 5-((hexanoyloxy)methyl)-2-furancarboxylate (HHMFC) and dihexyl 5,5'-(oxybis(methylene))bis(furan-2-carboxylate) (DHOBFC). The chemical structures of these prepared plasticizers were confirmed using Fourier transform infrared and nuclear magnetic resonance, and then, their plasticization effects on poly(vinyl chloride) (PVC) were also studied. As a result, HFCA-based plasticizers were miscible with PVC and exhibited excellent plasticization performances, compared with commercial dioctyl phthalate. It was noted that HHMFC had a much better plasticizing effect on the PVC film than DHOBFC; however, it displayed a poorer volatility resistance and exudation resistance, which could be attributed to its smaller molecular weight. Besides, because each rigid furan ring of the synthesized plasticizers contained one oxygen atom, the polarity of HFCA-based plasticizers was improved, which inhibited them from migrating from the PVC matrix into nonpolar solvents. Therefore, the HFCA-based plasticizers have good potential as primary plasticizers for PVC

Ultrathin UiO-66-NH2 polycrystalline membrane for CO2/CH4 separation

MOF membranes exhibit impressive performance in gas separation due to their large surface area, controllable pore size and unique affinity. Here, the ultrathin UiO-66-NH2 polycrystalline membranes with thickness of ∼320 nm are successfully prepared within 1 h using a combination of ultrasound-assisted and microwave synthesis strategies. During the reaction, high-density small MOF nuclei are produced by sodium formate ultrasound-assisted, which act as sufficient nucleation sites for heterogeneous nucleation during membrane growth, aiming for development of a continuous MOF membrane on the porous substrate. The obtained UiO-66-NH2 membrane shows an ideal CO2/CH4 selectivity of 40 due to the enhanced the interaction between CO2 molecules and the membrane. Moreover, the narrowed pore structure further hinders the diffusion of larger-sized molecules owing to -NH2 occupying the pore channels, resulting in elevated CO2/CH4 selectivity. Compared to many other MOF membranes, the UiO-66-NH2 polycrystalline membranes exhibit a well balance of gas permeance and CO2/CH4 selectivity, which presents a new route for CO2 capture

Ultra-Thin SnS2-Pt Nanocatalyst for Efficient Hydrogen Evolution Reaction

Transition-metal dichalcogenides (TMDs) materials have attracted much attention for hydrogen evolution reaction (HER) as a new catalyst, but they still have challenges in poor stability and high reaction over-potential. In this study, ultra-thin SnS2 nanocatalysts were synthesized by simple hydrothermal method, and low load of Pt was added to form stable SnS2-Pt-3 (the content of platinum is 0.5 wt %). The synergistic effect between ultra-thin SnS2 rich in active sites and individual dispersed Pt nanoclusters can significantly reduce the reaction barrier and further accelerate HER reaction kinetics. Hence, SnS2-Pt-3 exhibits a low overpotential of 210 mV at the current density of 10 mA cm−2. It is worth noting that SnS2-Pt-3 has a small Tafel slope (126 mV dec−1) in 0.5 M H2SO4, as well as stability. This work provides a new option for the application of TMDs materials in efficient hydrogen evolution reaction. Moreover, this method can be easily extended to other catalysts with desired two-dimensional materials