Bound and free water distribution in wood during water uptake and drying as measured by 1D magnetic resonance imaging

Knowledge on moisture transport in wood is important for understanding its utilization, durability and product quality. Moisture transport processes in wood can be studied by Nuclear Magnetic Resonance (NMR) imaging. By combining NMR imaging with relaxometry, the state of water within wood can be identified, i.e. water bound to the cell wall, and free water in the cell lumen/vessel. This paper presents how the transport of water can be monitored and quantified in terms of bound and free water during water uptake and drying. Three types of wood from softwood to hardwood were selected covering a range of low to high density wood; pine sapwood and oak and teak. A calibration is performed to determine the different water states in each different wood type and to convert the NMR signal into moisture content. For all wood types, water transport appeared to be internally limited during both uptake and drying. In case of water uptake, free water was observed only after the cell walls were saturated with bound water. In case of drying, the loss of bound water starts only after vanishing of free water, irrespective of the position. Obviously, there is always a local thermodynamic equilibrium of bound and free water for both uptake and drying. Finally, we determined the effective diffusion coefficient (Deff). Experimentally determined diffusion constants were compared with those derived by the diffusion models for conceptual understanding of transport mechanism. We found that diffusion in the cell wall fibers plays a critical role in the transport process

Osoyoos Sign Committee

Osoyoos sign committee in front of Osoyoos sign erected south of international boundary. Man kneeling on far left is Eric Lohlein

Moisture content of the coating determines the water permeability as measured by 1D magnetic resonance imaging

In addition to the desired aesthetical properties, a coating is applied to protect against weathering. A coating prevents moisture accumulation in wood by reducing the water uptake into the wood by its barrier function. The studies in the coating permeability has gained interest with the shift towards waterborne coatings, which make coatings intrinsically more sensitive to water. This paper presents the results of a Nuclear Magnetic Resonance (NMR) Imaging study on the influence of a coating’s moisture content on the permeability of a coating on wood. In this work, pine sapwood, oak, and teak were selected as wood types covering a whole range of low to high density wood types. Three transparent coatings were formulated: a solventborne alkyd, a waterborne alkyd and a waterborne acrylic. The aim of this study is to investigate how sensitive the permeability of coatings on wood against moisture during liquid water uptake and subsequent drying below Fiber Saturation Point. During both water uptake and subsequent drying, the coating limited transport was observed for the studied wood-coating combinations. The NMR profiles are used to calculate the water permeability of coatings on wood. We have demonstrated the direct relation of the permeability with the average water activity inside the coating, which is connected to the activities of both sides of the coating. We observed reasonably well correlation between the sorption isotherm of the coatings and the permeability, which indicates that the permeability variations are due to the amount of water present in the coating. Finally, we have shown that the permeability is not about the type of water vapour or liquid present at one side of the coating, it is all about the local moisture content in the coating

Dual functionality of conjugated polymer nanoparticles as an anticancer drug carrier and a fluorescent probe for cell imaging

\u3cp\u3eMultifunctional nanoparticles based on a green emitting, hydrophobic conjugated polymer, poly[(9,9-bis{propeny}fluorenyl-2,7-diyl)-co-(1,4-benzo-{2, 1,3}-thiodiazole)] (PPFBT), that acts both as a fluorescent reporter and a matrix to accommodate an anti-cancer compound, camptothecin (CPT), were prepared, characterized and their potential as a fluorescent probe for cell imaging and as a drug delivery vehicle were evaluated via in vitro cell assays. The cell viability of human hepatocellular carcinoma cell line (Huh7) was investigated in the absence and presence of CPT with sulforhodamine B (SRB) and real-time cell electronic sensing (RT-CES) cytotoxicity assays.\u3c/p\u3

Magnetic resonance imaging of the drying and wetting process of coatings on wood

As a result of the VOC regulations, a transition towards waterborne coatings has been made. Generally, waterborne coatings are intrinsically more sensitive to water. This higher sensitivity to water may negatively affect the durability of wood, due to microbiological growth. To prevent this, knowledge on the barrier properties of coatings is needed. Our studies focus on understanding the moisture transport through alkyd (solvent and waterborne) and acrylic model coating formulations applied on teak, oak and pine. One of the key research question focuses on the importance of the interface on the barrier properties (both wetting and drying) of the coating, e.g. due to grains raising and penetration. To answer this question, Magnetic Resonance Imaging on both the uncoated and the coated wood is applied. MRI signal relaxation analysis (T2) unravels whether water is free in the lumen or bound to the cell wall. Our results show that the moisture permeability depends on the specific combination of wood and coating, since the coating influences the moisture sorption of wood in different ways. For example, on pine sapwood, the acrylic coating increases the total drying time seven times compared to uncoated wood by sealing the surface