34 research outputs found
Investigation of starch hydration by 2D time domain NMR
Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and water was studied using the 2D time domain NMR. The proton spin-spin relaxation time T, and spin-lattice relaxation time T (selective and non-selective pulse sequences) were measured at room temperature. The observed spin relaxation results were analysed for exchange assuming a two-site exchange model (between water and solid matrix of starch). In this analysis we determined the intrinsic spin-lattice relaxation time for water protons (49 ms) and solid starch matrix protons (172 ms), as well as the water-starch magnetization exchange rate (86 s)
Study of Restricted Diffusion in Wood
An NMR study of restricted diffusion of water in Douglas-fir wood was undertaken using the pulsed field gradient method. The measurements were performed at 25 C and at two different moisture contents. Analysis of the results shows that the restricted diffusion of water molecules in this sample can be adequately described using a restricted diffusion model that considers diffusion to occur between infinite planar barriers. Two different barrier separations were incorporated into the model in order to obtain a good correspondence between the calculated and experimental results. Excellent agreement exists between parameters deduced from the NMR measurements and known anatomical data
Magnetic resonance in porous media: Recent progress
Recent years have seen significant progress in the NMR study of porous media from natural and industrial sources and of cultural significance such as paintings. This paper provides a brief outline of the recent technical development of NMR in this area. These advances are relevant for broad NMR applications in material characterization.open283
Thermal modification of wood and a complex study of its properties by magnetic resonance and other methods
© 2016, Springer-Verlag Berlin Heidelberg.Thermal modification of wood is an effective method to improve some of the properties of wood. It is reported on studies of vacuum thermal-treated wood species by magnetic resonance methods. Wood species such as Scots pine (Pinus sylvestris), birch (Betula pendula), Russian larch (Larix sibirica), Norway spruce (Picea abies), small-leaved lime (Tilia cordata) were vacuum treated by heat at 220 °C with various durations up to 8 h. This selection of wood species was investigated by electron paramagnetic resonance, nuclear magnetic resonance and microscopy methods before and after the thermal treatment. Electron paramagnetic resonance experiments revealed changes in the amount of free radicals in samples with the thermal treatment duration. Additional information on magnetic relaxation of 1H nuclei in samples at room temperature was obtained. Optical microscope analysis helped to detect structural changes in the thermally modified wood. Important properties of wood such as wood hardness and humidity absorption were also studied. The original results that were obtained correlate and complement each other, and clarify changes in the wood structure that appear with the heat treatment
Nuclear magnetic resonance multiwindow analysis of proton local fields and magnetization distribution in natural and deuterated mouse muscle.
The proton free-induction decays, spin-spin relaxation times, local fields in the rotating frame, and spin-lattice relaxation times in the laboratory and rotating frames, in natural and fully deuterated mouse muscle, are reported. Measurements were taken above and below freezing temperature and at two time windows on the free-induction decay. A comparative analysis show that the magnetization fractions deduced from the different experiments are in good agreement. The main conclusion is that the resolution of the (heterogeneous) muscle nuclear magnetic resonance (NMR) response is improved by the multiwindow analysis
Absolute moisture content determination of aspen wood below the fiber saturation point using pulsed NMR
Characterization of polyproline-water system by NMR spin grouping and exchange analysis
Proton NMR spin grouping experiments and measurements were performed in dry and hydrated polyproline powders. The results in the hydrated samples were analyzed for magnetization exchange using a linear three site (proline —— proline) exchange scenario. The intrinsic proline and water proton relaxation parameters as well as the exchange rates were obtained. All proline protons are effectively coupled to the water protons. Perhaps the most significant result is the observation, for the first time, of a very large spin-spin coupling rate between water protons and a small fraction of the polymer proton population