Current medical education facilities use simulation training to educate medical residents and other healthcare staff. These centers typically rely on single-use soft training devices that use ballistics gel to simulate human tissue but that must be discarded after a single training session. This not only is an environmental burden but amounts to a tremendous cost for training programs. As such, I have adapted a self-healing nanocomposite hydrogel to make surgical phantoms and other medical education mannequins reusable. This hydrogel has similar storage and loss moduli to human muscle tissue and is acoustically similar to human tissue. Failure testing of the hydrogel material simulating trainer use, i.e., cycles of needle punctures and overnight healing, demonstrated that the hydrogel trainer can be used up to 10 times with successful healing. The hydrogel is initially intended to replace single-session clinical trainers for ultrasound-guided central line placement, so I created a perfusable, more anatomically accurate trainer where the device can be pressurized with liquid to simulate human blood vessels and bleeding. In a blinded study of training staff within the Simulation Training Center at the University of California, San Diego, qualitative ultrasound evaluation indicated that clinical experts could not, upon initial evaluation, correctly determine which training devices had previously been punctured and healed. These data suggest that a self-healing nanocomposite hydrogel may be an alternative to current single-use soft training materials.

Understanding individual and interconnected processes of nitrogen transformations in soil would benefit from recent developments in non-invasive, quantitative measurement technologies coupled with visualization techniques. ‘N-sight’ is a new technique under development that relies on the use of analyte-specific sensors impregnated into thin gels. The gels are inserted between the soil and glass wall of a rhizotron box and form a equilibrium with the soil solution. Specific optics excite and detect the chemical sensors to quantitatively measure the soil analyte of interest. Multiple single point measurements are arranged into a two-dimensional matrix and converted with software into intuitive visual images. The N-sight technique is demonstrated by following changes in soil pH caused by urea hydrolyzing to ammonium-N. Depending on soil type, the N-sight technique shows that soil pH begins increasing in less than one hour following application of granular urea and reaches a peak pH of approximately 9.5 directly under the point of application. Dynamic changes in soil pH with time and at different distances from the urea granule is clearly demonstrated. Ammonia volatilized into the headspace of the rhizotron box correlates with the magnitude of soil pH changes. Comparative analysis between urea and urea treated with the urease inhibitor Agrotain (N-(n-butyl) thiophosphoric triamide) shows the inhibitor slows the rate and magnitude of soil pH changes and correlates with a strong reduction in ammonia volatilization. The N-sight technique could be developed to quantify and visualize urea, ammonium-N, oxygen and potentially other analytes relevant for understanding or influencing the soil nitrogen cycle.