排序方式: 共有23条查询结果,搜索用时 15 毫秒
21.
Mikko Karesoja Harri Jokinen Erno Karjalainen Petri Pulkkinen Mika Torkkeli Antti Soininen Janne Ruokolainen Heikki Tenhu 《Journal of polymer science. Part A, Polymer chemistry》2009,47(12):3086-3097
11‐(2‐Bromo‐2‐methyl)propionyl‐oxy‐undecyl trichlorosilane atom transfer radical polymerization (ATRP) initiator was covalently attached on montmorillonite clay platelets via silylation reactions. The initiator clay was used to polymerize butyl acrylate (BuA) and methyl methacrylate (MMA) on the clay surface. Polymerization was performed in bulk monomer solution or in DMSO. Polymer modified clay was mixed with a poly(BuA‐co‐MMA) matrix. Small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) showed that clay modified in DMSO gave exfoliated composites when mixed with the matrix copolymer. Mechanical properties of the composites were studied by dynamic mechanical thermal analysis (DMTA). The results showed that the mechanical properties were improved as a function of clay content, as well with an increasing homogeneity of the nanocomposite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3086–3097, 2009 相似文献
22.
Otto Pulkkinen 《Journal of statistical physics》2007,128(6):1289-1305
The stationary states of boundary driven zero-range processes in random media with quenched disorder are examined, and the
motion of a tagged particle is analyzed. For symmetric transition rates, also known as the random barrier model, the stationary
state is found to be trivial in absence of boundary drive. Out of equilibrium, two further cases are distinguished according
to the tail of the disorder distribution. For strong disorder, the fugacity profiles are found to be governed by the paths
of normalized α-stable subordinators. The expectations of integrated functions of the tagged particle position are calculated for three types
of routes. 相似文献
23.
Hannes Warlo Katerina Machacova Nenne Nordstrom Martin Maier Thomas Laemmel Aappo Roos 《International journal of environmental analytical chemistry》2013,93(11):1030-1037
ABSTRACTProduction and consumption of methane (CH4) and nitrous oxide (N2O) in soils have a strong influence on global greenhouse gases (GHG) budgets. Therefore, it is crucial to precisely measure GHG fluxes at the soil–atmosphere interface. In upland soils, CH4 and N2O can be consumed by microbiological processes, and the respective concentrations can be lower than in the atmosphere, demanding highly sensitive gas analysing systems. Traditionally, soil air is sampled in vials and analysed in the laboratory by gas chromatography (GC). During the last decade, different technologies have been developed that allowed to build portable gas analysers that are able to measure sub-ambient gas concentration directly in the field. Here, we compared sub-ambient to ambient CH4 and N2O concentration values from four portable devices using different measurement technologies (a portable GHG analyser based on laser absorption spectroscopy [LAS], two portable Fourier transform infrared spectroscopy [FTIR] devices and a field gas analyser using photoacoustic spectroscopy [PAS]) to traditional GC analysis in the laboratory (a GC system equipped with a flame ionisation detector [GC-FID] and an electron capture detector [GC-ECD]). The accuracy and precision of photoacoustic spectroscopy measurements are strongly influenced by the water vapour content and non-target gases in the sampling air. We used an advanced set-up for a widely used PAS analyser enabling N2O measurements at sub-ambient concentrations with similar precision and accuracy as the GC-ECD system. Measurements of CH4 and N2O by FTIR and LAS devices were in good agreement with the GC systems. We conclude that the portable devices are suitable for studies of GHG fluxes in the field. Thanks to their universal and portable character, LAS, PAS and FTIR devices represent useful alternatives to currently used technologies for field studies. 相似文献