Quantitative NME microscopy of iron transport in methanogenic aggregates

Transport of micronutrients (iron, cobalt, nickel, etc.) within biofilms matrixes such as methanogenic granules is of high importance, because these are either essential or toxic for the microorganisms living inside the biofilm. The present study demonstrates quantitative measurements of metal transport inside these biofilms using T1 weighted 3D RARE. It is shown that iron(II)-EDTA diffusion within the granule is independent of direction or the inner structure of the granules. Assuming position dependence of the spin-lattice relaxivity, Fick’s law for diffusion in a sphere can be applied to simulate the diffusion within the methanogenic granules under investigation. A relatively low diffusion coefficient of 2.5*10-11 m2·s-1 was obtained for iron diffusion within the methanogenic granul

MRI in soils: determination of water concent changes due to root water uptake by means of a multi-slice-multi-echo sequence (MSME)

Root water uptake by ricinus communis (castor bean) in fine sand was investigated using MRI with multiecho sampling. Before starting the experiments the plants germinated and grew for 3 weeks in a cylindrical container with a diameter of 9 cm. Immediately before the MRI experiments started, the containers were water-saturated and sealed, so water content changes were only caused by root water uptake. In continuation of a preceding work, where we applied SPRITE we tested a multi-echo multi-slice sequence (MSME). In this approach, the water content was imaged by setting TE = 6.76 ms and nE = 128 with an isotropic resolution of 3.1mm. We calculated the water content maps by biexponential fitting of the multi-slice echo train data and normalisation on reference cuvettes filled with glass beads and 1 mM NiCl2 solution. The water content determination was validated by comparing to mean gravimetric water content measurements. By coregistration with the root architecture, visualised by a 3D fast spin echo sequence (RARE), we conclude that the largest water content changes occurred in the neighbourhood of the roots and in the upper layers of the soil

NMR microimaging of fluid flowin model string-type reactors

Magnetic resonance microimaging (MRM) was employed to obtain quantitative velocity maps of water flowing in the channels possessing unconventional cross-section shapes formed by a bundle of parallel fibers within a tubular string-type reactor. The maps obtained demonstrate the presence of large amounts of an almost stagnant liquid in the stretched corners of the cross-sections representing distorted triangles or squares. This fact together with the irregularity of the filaments packing in the model string-type reactor was demonstrated to lead to a broad residence time distributions (RTDs) for liquid flow. Next, the pulsed field gradient NMR (PFG NMR) technique was employed to compare transport of water with that of butane gas in the same model string-type reactor. The experimentally measured average propagators (travel distance probability density functions) have demonstrated that Taylor dispersion can lead to much better RTDs for gas as compared to liquid in channels with sub-millimeter equivalent diameters. The PFG NMR data were compared with the RTD obtained using the conventional tracer time-of-flight transient response method. It is concluded that due to the differences in the quantities actually measured by the two techniques, and the significant differences in the measurement length scales (microns to 1–2 cm for NMR/MRM, tens of centimeters for transient response methods), there is no reliable way of directly comparing these results. The information obtained by NMR/MRM and more conventional techniques such as time-of-flight should be considered as complementary. In particular, NMR/MRM can reveal the reasons for the observed overall reactor performance by providing access to the transport processes on short length scales inside the reactor and by revealing structure–transport interrelation

Investigation on the influence of pre-treatments on drying behaviour of broccoli by MRI experiments

Abstract: Magnetic Resonance Imaging (MRI) allows the monitoring of internal moisture content of food products during drying non-destructively. In an experimental set-up with continuous and controlled hot air supply, the internal moisture distribution of broccoli with different pre-treatments are measured during drying. Moisture distribution, drying rate and shrinkage are compared and analyzed quantitatively. MRI results indicated that for fresh broccoli stalks the moisture content in the core of the sample increased after some hours of drying. With pre-treatments as peeling, blanching or freezing the moisture transport barrier in the skin of the broccoli sample was reduced. Shrinkage was uniform for most of the pre-treated samples and the moisture increment in the core did not occur. It was also found that with these pre-treatments progress of drying enhanced significantly. Therefore, from an drying efficiency and economic point of view, pre-treatments prior to drying offer important opportunities. Keywords: MRI, hot air drying, broccoli stalk, increased moisture content, pre-treatment

Moisture distribution in broccoli: measurements by MRI hot air drying experiments

The internal moisture distribution that arise in food products during drying, is a key factor for the retention of quality attributes. To reveal the course of moisture content in a product, internal moisture profiles in broccoli florets are measured by MRI imaging during drying experiments with controlled air flow and temperature. The 3D images concern a matrix size of 64×64×64 elements. Signal intensity is converted to product moisture content with a linear relationship, while taking a minimum detectable moisture content of 0.3 kg water/ kg dry matter into account. Moisture content as a function of time is presented for a 2D cross sectional area in the middle of a broccoli sample. The average moisture contents for the cross sectional area obtained from the MRI imaging are compared with spatial model simulations for the moisture distribution. In that model the effective diffusion coefficient is based on the Free Volume Theory. This theory has the advantage that the changed mobility of water in the product during drying is taken into account and the theory also predicts the moisture transport in the porous broccoli floret. Key parameters for the Free Volume Theory are estimated by fitting to the experimental MRI results and the effective diffusion coefficient is given as a function of the product water content

Nonlinear internal waves over New Jersey's continental shelf

Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): C03022, doi:10.1029/2010JC006332.Ship and mooring data collected off the coast of New Jersey are used to describe the nonlinear internal wave (NLIW) field and the background oceanographic conditions that formed the waveguide on the shelf. The subinertial, inertial, and tidal circulation are described in detail, and the background fluid state is characterized using the coefficients of the extended Korteweg–de Vries equation. The utility of this type of analysis is demonstrated in description of an amplitude-limited, flat wave. NLIWs observed over most of the month had typical displacements of −8 m, but waves observed from 17–21 August were almost twice as large with displacements near −15 m. During most of the month, wave packets occurred irregularly at a fixed location, and often more than one packet was observed per M2 tidal period. In contrast, the arrival times of the large-amplitude wave groups observed over 17–21 August were more closely phased with the barotropic tide. The time span in which the largest NLIWs were observed corresponded to neap barotropic conditions, but when the shoreward baroclinic energy flux was elevated. During the time of large NLIWs, near-inertial waves were a dominate contributor to the internal motions on the shelf and apparently regulated wave formation, as destructive/constructive modulation of the M2 internal tide by the inertial wavefield at the shelf break corresponded to stronger/weaker NLIWs on the shelf.This work was funded by the Office of Naval Research

Quantitative permeability imaging of plant tissues

A method for mapping tissue permeability based on time-dependent diffusion measurements is presented. A pulsed field gradient sequence to measure the diffusion encoding time dependence of the diffusion coefficients based on the detection of stimulated spin echoes to enable long diffusion times is combined with a turbo spin echo sequence for fast NMR imaging (MRI). A fitting function is suggested to describe the time dependence of the apparent diffusion constant in porous (bio-)materials, even if the time range of the apparent diffusion coefficient is limited due to relaxation of the magnetization. The method is demonstrated by characterizing anisotropic cell dimensions and permeability on a subpixel level of different tissues of a carrot (Daucus carota) taproot in the radial and axial directions

Building your own mountain: the effects, limits, and drawbacks of cold-water coral ecosystem engineering

Framework-forming cold-water corals (CWCs) are ecosystem engineers that build mounds in the deep sea that can be up to several hundred metres high. The effect of the presence of cold-water coral mounds on their surroundings is typically difficult to separate from environmental factors that are not affected by the mounds. We investigated the environmental control on and the importance of ecosystem engineering for cold-water coral reefs using annotated video transect data, spatial variables (MEMs), and hydrodynamic model outputs in a redundancy analysis and with variance partitioning. Using available hydrodynamic simulations with cold-water coral mounds and simulations where the mounds were artificially removed, we investigated the effect of coral mound ecosystem engineering on the spatial configuration of reef habitat and discriminated which environmental factors are and which are not affected by the mounds. We find that downward velocities in winter, related to non-engineered environmental factors, e.g. deep winter mixing and dense-water cascading, cause substantial differences in reef cover at the broadest spatial scale (20–30 km). Such hydrodynamic processes that stimulate the food supply towards the corals in winter seem more important for the reefs than cold-water coral mound engineering or similar hydrodynamic processes in summer. While the ecosystem-engineering effect of cold-water corals is frequently discussed, our results also highlight the importance of non-engineered environmental processes. We further find that, due to the interaction between the coral mound and the water flow, different hydrodynamic zones are found on coral mounds that likely determine the typical benthic zonations of coral rubble at the mound foot, the dead coral framework on the mound flanks, and the living corals near the summit. Moreover, we suggest that a so-called Massenerhebung effect (well known for terrestrial mountains) exists, meaning that benthic zonation depends on the location of the mound rather than on the height above the seafloor or water depth. Our finding that ecosystem engineering determines the configuration of benthic habitats on cold-water coral mounds implies that cold-water corals cannot grow at deeper depths on the mounds to avoid the adverse effects of climate change.</p