Novel agarose-dextran hydrogels were synthesized and their suitability as experimental models of glomerular basement membrane was examined by measuring their Darcy (hydraulic) permeabilities (kappa). Immobilization of large dextran molecules in agarose was achieved by electron beam irradiation. Composite gels were made with agarose volume fractions (phi(a)) of 0.04 or 0.08 and dextran volume fractions (phi(d)) ranging from 0 to 0.02 (fiber volume/gel volume), using either of two dextran molecular weights (500 or 2000). At either agarose concentration and for either size of dextran, kappa decreased markedly as the amount of dextran was increased. Statistically significant deviations from the value of kappa for pure agarose were obtained for remarkably small volume fractions of dextran: phi(d) > or = 0.0003 for phi(a) = 0.04 and phi(d) > or = 0.001 for phi(a) = 0.08. The Darcy permeabilities were much more sensitive to phi(d) than to phi(a), and were as much as 26 times smaller than those of pure agarose. Although phi(d) was an important variable, dextran molecular weight was not. The effects of dextran addition on kappa were described fairly well using simple structural idealizations. At high agarose concentrations, the dextran chains behaved as fine fibers interspersed among coarse agarose fibrils, whereas, at low concentrations, the dextran molecules began to resemble spherical obstacles embedded in agarose gels. The ability to achieve physiologically relevant Darcy permeabilities with these materials (as low as 1.6 nm2) makes them an attractive experimental model for glomerular basement membrane and possibly other extracellular matrices.

This article presents experimental and computational studies of a phase shifting photolithographic technique that uses binary elastomeric phase masks in conformal contact with layers of photoresist. The work incorporates optimized masks formed by casting and curing prepolymers to the elastomer poly͑dimethylsiloxane͒ against anisotropically etched structures of single crystal silicon on SiO 2 / Si. Scanning optical microscopy and full-vector finite element computations reveal the important near field and proximity optical effects. Representative structures fabricated with this technique, including several that exploit subtle features in the intensity distributions, illustrate some of the capabilities.

Our findings suggest potential for PPi, administered during PD, to prevent the development of VC and to potentially extend the life of ESRD patients.

A web-based Patient Accessible Electronic Health Record was designed for patients with congenital cardiac disease. The adoption rate was high, and utilisation patterns suggest that the Electronic Health Record could become a useful tool for health information exchange.

A theory was developed to describe the equilibrium partitioning of a flexible polymeric solute between a dilute solution and a medium consisting of a randomly oriented array of fibers (e.g., a fibrous membrane or gel). The fibers were regarded as long, rigid cylinders, and the solute was modeled as a chain consisting of n mass points joined by n − 1 rectilinear segments. Results were obtained for freely jointed chains and for chains with fixed bond angles, using a combination of analytical and computational (e.g., Monte Carlo) techniques. The predicted partition coefficient (Φ, the solute concentration in the fibrous material divided by that in the bulk solution) proved to be sensitive to the number of fibers included; typically, 50 or more nearest-neighboring fibers were needed to obtain a convergent result. The values of Φ decreased as fiber volume fraction, molecular size, or number of mass points was increased selectively. As the bond angle was increased from 0° (a chain folding back on itself) to 180° (a rodlike chain), Φ first decreased and then increased. The model predictions agreed reasonably well with literature partitioning data for various polymeric solutes in hydrogels, especially when the radius of gyration was no more than a few times the fiber radius. With the radius of gyration specified, the model predictions were fairly insensitive to whether the bond angle was fixed or random.