Water Diffusion and Uptake in Injectable ETTMP/PEGDA Hydrogels.

Differential scanning calorimetry (DSC) and pulsed field gradient spin echo nuclear magnetic resonance (PFGSE NMR) were used to characterize water in hydrogels of ethoxylated trimethylolpropane tri-3-mercaptopropionate (ETTMP) and poly(ethylene glycol) diacrylate (PEGDA). Freezable and nonfreezable water were quantified using DSC; water diffusion coefficients were measured using PFGSE NMR. No freezable water (free or intermediate) was detected from DSC for hydrogels of 0.

A two-region transport model for interpreting T-T measurements in complex systems.

A 1D two region coupled pore model with discrete pore coupling is developed to elucidate the eigenmode interactions in regions with different surface relaxivity. Numerical solution of the model and simulation of the correlation experiment for varying surface relaxivity, pore connectivity and pore size ratio indicate the role of negative eigenmodes and overlap of T and T eigenmodes in generating a time domain signal increase with inversion recovery time, t. The eigenmodes and eigenfunctions are considered in detail providing connection between the mathematical model and the diffusion dynamics and spin physics of the system.

Flow velocity maps measured by nuclear magnetic resonance in medical intravenous catheter needleless connectors.

This work explains the motivation, advantages, and novel approach of using velocity magnetic resonance imaging (MRI) for studying the hydrodynamics in a complicated structural biomedical device such as an intravenous catheter needleless connector (NC). MRI was applied as a non-invasive and non-destructive technique to evaluate the fluid dynamics associated with various internal designs of the NC. Spatial velocity maps of fluid flow at specific locations within these medical devices were acquired.

Quantifying NMR relaxation correlation and exchange in articular cartilage with time domain analysis.

Measured nuclear magnetic resonance (NMR) transverse relaxation data in articular cartilage has been shown to be multi-exponential and correlated to the health of the tissue. The observed relaxation rates are dependent on experimental parameters such as solvent, data acquisition methods, data analysis methods, and alignment to the magnetic field. In this study, we show that diffusive exchange occurs in porcine articular cartilage and impacts the observed relaxation rates in T-T correlation experiments.

Unused medications and disposal patterns at home: Findings from a Medicare patient survey and claims data.

Objective: To examine what medications are most frequently left unused by patients, how much is left unused, and how these medications are disposed of among Medicare beneficiaries.

Design: Secondary data analysis combining insurance claims and telephone survey data of Medicare Advantage members.

Setting: Regional health plan in Central Pennsylvania.

A microfluidic method to measure small molecule diffusion in hydrogels.

Drug release from a fluid-contacting biomaterial is simulated using a microfluidic device with a channel defined by solute-loaded hydrogel; as water is pumped through the channel, solute transfers from the hydrogel into the water. Optical analysis of in-situ hydrogels, characterization of the microfluidic device effluent, and NMR methods were used to find diffusion coefficients of several dyes (model drugs) in poly(ethylene glycol) diacrylate (PEG-DA) hydrogels. Diffusion coefficients for methylene blue and sulforhodamine 101 in PEG-DA calculated using the three methods are in good agreement; both dyes are mobile in the hydrogel and elute from the hydrogel at the aqueous channel interface.

Critical review of coupled flux formulations for clay membranes based on nonequilibrium thermodynamics.

Extensive research conducted over the past several decades has indicated that semipermeable membrane behavior (i.e., the ability of a porous medium to restrict the passage of solutes) may have a significant influence on solute migration through a wide variety of clay-rich soils, including both natural clay formations (aquitards, aquicludes) and engineered clay barriers (e.

Magnetic resonance analysis of capillary formation reaction front dynamics in alginate gels.

The formation of heterogeneous structures in biopolymer gels is of current interest for biomedical applications and is of fundamental interest to understanding the molecular level origins of structures generated from disordered solutions by reactions. The cation-mediated physical gelation of alginate by calcium and copper is analyzed using magnetic resonance measurements of spatially resolved molecular dynamics during gel front propagation. Relaxation time and pulse-field gradient methods are applied to determine the impact of ion front motion on molecular translational dynamics.

Influence of adsorption on phenol transport through soil-bentonite vertical barriers amended with activated carbon.

The potential for enhanced containment of phenol by soil-bentonite (SB) vertical barriers amended with activated carbon (AC) was investigated. Results of batch equilibrium adsorption tests on model SB backfills amended with 0-10 wt.% granular AC (GAC) or powdered AC (PAC) illustrate that the backfills exhibited nonlinear adsorption behavior that was described well by both the Freundlich and Tóth adsorption models.

Advancement in the modeling of pressure-flow for the guidance of development and scale-up of commercial-scale biopharmaceutical chromatography.

This paper details the advancements made in the modeling of open column and packed bed pressure-flow. The theoretical description is a one-dimensional elasticity model. By accounting for the loss of intra-particle porosity through empiricism, and by systematically selecting the functional form of the elastic modulus from stress-strain data, this model can accurately predict several kinds of large-scale behavior from small-scale data: packed pressure-flow, open column pressure-flow, and critical velocity.

Toward a robust model of packing and scale-up for chromatographic beds. 2. Flow packing.

We developed and evaluated a model for predicting the flow packing of nonrigid chromatographic resins. The model is based on elasticity theory and accounts for resin rigidity and column diameter. When a modulus determined from a standard mechanical compression (consolidation) test is used, the model captures the primary phenomena of the scale-up process.

Toward a robust model of packing and scale-up for chromatographic beds. 1. Mechanical compression.

The packing of compressible biochromatographic resins at large scale suffers from a poor understanding of how column packing method, resin properties, and column geometry impact column performance. To improve understanding, we develop and evaluate a one-dimensional, continuum mechanics model of column packing by mechanical compression. We show that the model can quantitatively predict the change in bed height, applied stress, and internal axial porosity profile without adjustable parameters when the modulus and wall friction coefficients are determined independently.

Analysis of bacterial random motility in a porous medium using magnetic resonance imaging and immunomagnetic labeling.

In this study, we demonstrate the application of immunomagnetic labeling and magnetic resonance imaging (MRI) for the noninvasive visualization of changes in bacterial density distributions as a function of time in a water-saturated porous medium. Magnetite particles (50-60 nm diameter) were attached via a monoclonal antibody to the surface' of Escherichia coli K12 NR50 cells. The cells maintained their motility after labeling, and the presence of the magnetite did not significantly alter cell swimming speed.