Previous studies have tested the “vernal dam” hypothesis of spring ephemeral herbs in hardwood forests. The desert annual is a component of the desert ecosystem that takes advantage of water ...resources and temperature conditions during the rainy season to rapidly complete its life cycle within several months. To understand the role desert annual/ephemeral plants play in nutrient flow, we studied vegetation cover, nitrogen content and litter production of annual plants and litter decomposition rate in plant communities dominated by four shrubs (Haloxlon ammodendron, Hedysarum scoparium, Calligonum mongolicum, and Nitraria tangutorum) and two dominant annuals (Agriophyllum squarrosum and Halogeton arachnoideus Moq) in Minqin, northwestern China. Results indicate that over half of the total vegetation cover was provided by annuals. Annuals also took up a large amount of nitrogen (0.46-3.78 g N m⁻²) along the oasis-desert ecotone. Litter production and nutrient content were higher in areas dominated by annual plants than in areas dominated by shrubs. Furthermore, the litter decomposition rate of the annuals was higher than that of the shrubs, except for the shrub H. ammodendron, although almost all of the litter's carbon (C) and nitrogen (N) remained after 6 months of decomposition. Without the annuals, more nutrients and rainwater might be lost through leaching or dust transfer caused by the wind erosion. In addition, green twigs of the annuals are the food for some animals, we found some green twigs and litter from annuals left in front of gerbil and rabbit burrows, sometimes even blocking these burrows. Thus, desert summer annuals, like nutrient reservoirs and providers, take up nutrients during the rainy season, providing some animals and microbes with food, and finally release these nutrients after death.
Regioselective control by a catalyst switch in palladium-catalyzed benzylallylation of arylethylidene malononitriles (α-benzyl-β-allylation versus α-allyl-β-benzylation) is described. The ...three-component reaction of 2-(bromomethyl)naphthalenes, arylethylidene malononitriles, and allyltributylstannane proceeds smoothly with palladium nanoparticles as a catalyst to provide α-benzyl-β-allylation products in good yields. The regioselectivity of the benzylallylation reaction is completely overturned with Pd(PPh3)4 as the catalyst instead of palladium nanoparticles to obtain α-allyl-β-benzylation products in moderate to good yields.
The three-component reaction of 2-(bromomethyl)naphthalenes, arylethylidene malononitriles, and allyltributylstannane proceeds smoothly in the presence of palladium nanoparticles as a catalyst to provide α-benzyl-β-allylation products in good yields. The regioselectivity of the benzylallylation reaction is completely overturned with Pd(PPh3)4 as the catalyst to obtain α-allyl-β-benzylation products in moderate to good yields. Display omitted
•Achieved selective synthesis of α-benzyl-β-allylation products 3 using palladium nanoparticle catalyst.•Achieved aselective synthesis of α-allyl-β-benzylation products 4 using Pd(PPh3)4 catalyst.•Provided novel and general methods for the bisfunctionalization of activated olefin compounds.
Abstract Risk factors for coronary heart disease can reduce the number of endothelial progenitor cells (EPCs) and impair EPC function, thus hindering their utility in the treatment of cardiovascular ...diseases. In the present study, we began exploring the feasibility of genetic modification of EPCs with hepatocyte growth factor (HGF) to counter the effects of these risk factors and enhance the biological functions of EPCs. The effects of HGF transfection on proliferation, migration and angiogenesis of EPCs were investigated. Additionally, the role of ERK1/2 in this process was evaluated through the observation of ERK1/2 and ERK1/2 phosphorylation as well as by pharmacological analysis. Finally, we evaluated the effect of HGF-transfected EPCs (HGF-EPCs) on neointima formation after balloon-induced arterial injury in hypercholesterolemic rats. Our data showed that EPCs transfected with the HGF gene released high levels of soluble HGF protein, which were maintained for at least nine days. Transfection with HGF also enhanced the proliferative, migratory and angiogenic capabilities of EPCs, and promoted the activation of ERK1/2 without affecting its expression. ERK1/2 blockade by the chemical inhibitor PD98059 partially inhibited these effects. In hypercholesterolemic rats, HGF-EPCs homed to the site of vascular injury at a significantly higher rate than did EPCs without the exogenous HGF gene. Furthermore, systemically applied HGF-EPCs were more effective in decreasing neointima formation and increasing re-endothelialization. These data suggest that gene delivery combined with EPC transplant may be a practical and promising therapy for the prevention of neointimal formation after vascular injury.
This study was designed to detect aberrant p16 promoter methylation in the serum of patients with colorectal cancer (CRC) and to explore the possibility of using this assay in early detection or as a ...prognostic marker of CRC patients.
Methylation-specific PCR was used to detect p16 methylation in DNA extracted from 52 CRCs and matching serum samples and control serum samples from 34 patients with adenomatous polyps and 10 healthy individuals. The association of p16 hypermethylation in serum DNA of CRC patients with clinicopathological characteristics was then analyzed.
P16 hypermethylation was found in 20 of 52 (38%) CRCs. Among the 20 cases with aberrant methylation in the tumor tissues, similar changes were also detected in the serum of 14 (70%) cases. No methylated p16 sequences were detected in the peripheral serum of the other 32 CRC cases without these changes in the tumor, in 34 patients with adenomatous polyps, or in 10 healthy control subjects. Clinicopathological analysis revealed that p16 methylation in serum was significantly associated with later Dukes' stage (P = 0.03).
This assay offers a potential means for the serum-based detection and/or monitoring of CRC patients.
Biological invasion represents one of the most serious threats to biodiversity, and invasion ecology research has become one of the central issues of contemporary environmental science. However, the ...relative role of soil development as correlated with succession in influencing variation in invasion resistance has seldom been examined. We hypothesized that the invasion potential of exotic plants depends on soil conditions. In this study, we explored variation among soils of three forest types in their resistance to invasion by Mikania micrantha H.B.K. in lower subtropical China; this species is one of the top ten most invasive weeds in the world. In model systems of soils from different forests, M. micrantha performed worst on undisturbed late-successional stage forest (monsoon evergreen broadleaf forest, MEBF) soils and did not appear to take advantage of abundant soil nutrients. These results could reflect that a potential inhibitory effect was driven by MEBF soil. Plant litter is an important component of soils, litter bioassay and addition experiments demonstrated native plant species from different forests differentially confer invasion resistance and affect the performance of exotic plants. Naturally, other factors such as the relative abundances of nutrients, microbial feedbacks, could have contributed to these results as well. Our results challenge the notion that forests are not immune to invasion and suggest that maintaining late-successional plant communities in lower subtropical China, which could be related to increased productivity and stability, should be a primary objective of land managers.
Plasma generator is a core component in an electrothermal-chemical（ETC） launcher. Its work state directly influences the launch efficiency of a system. The interaction between plasma and propellants ...is a very important mechanism in ETC technology. Based on the transient radiation model and open air plasma jet experiment, the mechanism of plasma ignition process is analyzed. Results show that the surface temperature of local solid propellant grain can quickly achieve the ignition temperature under the action of early transient plasma radiation. But it needs enough time to maintain the high energy flow to make self-sustained combustion of solid propellant grains. Because of the limited space characteristics of transient radiation, the near-field propellant grains can gain enough energy by the strong transient radiation to be ignited and achieve self-sustained combustion. The far-field propellant grains mainly gain the energy by the activated particles in plasma jet to be ignited and self-sustained combustion. Experiments show that plasma jet always has a high flow velocity in the area of the cartridge. Compared with conventional ignition, the solid propellant grains can obtain more quick and uniform ignition and self-sustained combustion by this kind of ablation controlled arc（ACA） plasma via energy skin effect of propellant grains, pre-heat temperature mechanism and high efficient jet diffusion.
An efficient method for the synthesis of 5-vinyl-2-norbornene from cyclopentadiene and 1,3-butadiene was developed.The Diels-Alder reaction of cyclopentadiene with 1,3-butadiene proceeded smoothly in ...supercritical carbon dioxide in the absence of any polymerization inhibitor to produce the corresponding5-vinyl-2-norbornene in satisfactory yield with high selectivity.
Abstract
To demonstrate the relationship between the type of working gas and the efficiency of plasma cleaning, the kinetic energy of the incident ions was controlled by adjusting the bias, and the ...effect of different ion sources on the sputtering yield under the same bias was compared. The plasma flow generated by glow discharge was used to clean the sample surface to evaluate the plasma cleaning efficiency. Scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), x-ray Powder Diffraction (XRD), Ultraviolet-visible Spectrophotometer (UV), and Surface Profiler were used to characterize the surface morphology, element types, phase composition, specular reflectance, and three-dimensional (3D) morphology before and after plasma cleaning. The results show that the sputtering yield increases with the increase of bias, and when the bias value is lower than 400 V, the mass of the samples has almost no change before and after cleaning. It takes more energy to remove the surface oxide than the pure metal copper. The results also show that argon plasma has a better effect on removing pollutants on the sample surface than nitrogen plasma. However, a long time of plasma cleaning is often accompanied by re-deposition. The changes in copper reflectance induced by plasma cleaning are also discussed.
J. Neurochem. (2011) 119, 342–353.
Action potential (AP) patterns and dopamine (DA) release are known to correlate with rewarding behaviors, but how codes of AP bursts translate into DA release in ...vivo remains elusive. Here, a given AP pattern was defined by four codes, termed total AP number, frequency, number of AP bursts, and interburst time N, f, b, i.. The ‘burst effect’ was calculated by the ratio (γ) of DA overflow by multiple bursts to that of a single burst when total AP number was fixed. By stimulating the medial forebrain bundle using AP codes at either physiological (20 Hz) or supraphysiological (80 Hz) frequencies, we found that DA was released from two kinetically distinct vesicle pools, the fast‐releasable pool (FRP) and prolonged‐releasable pool (PRP), in striatal dopaminergic terminals in vivo. We examined the effects of vesicle pools on AP‐pattern dependent DA overflow and found, with given ‘burst codes’ b = 8, i = 0.5 s, a large total AP number N = 768, f = 80 Hz produced a facilitating burst‐effect (γb8/b1 = 126 ± 3%), while a small total AP number N = 96, 80 Hz triggered a depressing‐burst‐effect (γb8/b1 = 29 ± 4%). Furthermore, we found that the PRP (but not the FRP) predominantly contributed to the facilitating‐burst‐effect and the FRP played an important role in the depressing‐burst effect. Thus, our results suggest that striatal DA release captures pre‐synaptic AP pattern information through different releasable pools.
Data assimilation is an efficient way to improve the simulation/prediction accuracy in many fields of geosciences especially in meteorological and hydrological applications. This study takes ...unscented particle filter (UPF) as an example to test its performance at different two probability distribution, Gaussian and Uniform distributions with two different assimilation frequencies experiments (1) assimilating hourly in situ soil surface temperature, (2) assimilating the original Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) once per day. The numerical experiment results show that the filter performs better when increasing the assimilation frequency. In addition, UPF is efficient for improving the soil variables (e.g., soil temperature) simulation/prediction accuracy, though it is not sensitive to the probability distribution for observation error in soil temperature assimilation.
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