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101.
Dörte Diehl Jette Schwarz Marc-O. Goebel Susanne K. Woche Tatjana Schneckenburger Jaane Krüger Anastasia Shchegolikhina Bernd Marschner Friederike Lang Sören Thiele-Bruhn Jörg Bachmann Gabriele E. Schaumann 《Journal of Thermal Analysis and Calorimetry》2014,118(2):1203-1213
Multivalent cations are suggested to influence the supramolecular structure of soil organic matter (SOM) via inter- and intra-molecular interactions with SOM functional groups. In this study, we tested the combined effect of cations, temperature treatment, and isothermal aging on SOM matrix properties. Samples from a peat and a mineral soil were either enriched with Na, Ca, and Al or desalinated in batch experiments. After treatment at 25, 40, 60, and 105 °C and after different periods of aging at 19 °C and 31 % relative humidity, we investigated the physicochemical matrix stability and the thermal stability against combustion. We hypothesized that multivalent cations stabilize the SOM matrix, that these structures disrupt at elevated temperatures, and that aging leads to an increase in matrix stability. The results show that cation-specific effects on matrix rigidity started to evolve in the peat only after 8 weeks of aging and were significantly lower than the temperature effects. Temperature treatment above 40 °C caused a non (or not immediately) reversible loss of water molecule bridges (WaMB) and above 60 °C a partly reversible melting process probably of semi-crystalline poly(methylene). Thermal stability increased with increasing cation valence and degree of protonation and was much less affected by temperature. Generally, Na-treated and control samples revealed lower thermal stability and lower increase in matrix rigidity with aging than those treated with Ca, Al, and H. We conclude that drying at elevated temperatures (>40 °C) may irreversibly change SOM structure via disruption of labile cross-links and melting of semi-crystalline domains. 相似文献
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A radial hydrodynamic model is used to investigate the radiative thermal instability in the scrape-off layer by applying a linear stability analysis of existing equilibrium states. Phase space trajectories are analyzed to derive conditions of their existence and bifurcation. Equilibrium profiles are calculated for the cases of homogeneous plasma temperature, plasma density and self-consistency. Unstable perturbations, localized in the scrape-off layer, may lead to a strongly radiating detached plasma belt. 相似文献
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In part I of our paper [1] a kinetic theory of the influence of neutral particle sources on the dynamics of tokamak plasmas has been developed and the general solution of this problem has been given for an arbitrary source function. By the use of these results we calculate in this part II the particle's distribution function for different simple source functions. In the case of recycling perpendicular to the limiter surface we derive analytical expressions for the charge density, the induced electric potential and the anomaleous electron density flux transverse to the magnetic field. 相似文献
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