Use of steady-state hydraulic tomography to inform the selection of a chaotic advection system.

The concept of chaotic advection is a novel approach that has the potential to overcome some of the challenges associated with mixing of reagents that commonly occur when injection based in situ treatment techniques are used. The rotated potential mixing (RPM) flow system is one configuration which has been theorized to achieve chaotic advection in porous media, and enhance reagent mixing by periodically re-oriented dipole pumping at a series of radial wells. Prior to field implementation of chaotic advection, the selection of an RPM flow protocol will likely require a numerical model that can adequately represent groundwater flow within the zone of interest. As expected, the hydraulic conductivity (K) field is the most critical input requirement for the selected groundwater flow model. Hydraulic tomography (HT) is an innovative characterization approach that has shown potential to provide information on a K field. In this investigation, we explored whether the same well system required to invoke chaotic advection can also be applied in a HT analysis, and evaluated the use of the generated K tomogram for the selection of RPM flow parameters that can enhance reagent mixing. A series of dipole pumping tests were conducted within an area of interest as defined by the limits of the circular network of eight injection/extraction wells used to invoke chaotic advection. Hydraulic head data collected from independent dipole pumping tests were used in an inverse model to perform steady-state hydraulic tomography (SSHT) analysis to generate a K tomogram. Both the K tomogram and an effective parameter approach (i.e., a single K value assigned across the entire spatial domain as determined by single well pumping and slug tests) produced estimates of hydraulic head that closely resembled those observed due to the relative homogeneous nature of the aquifer and the small spatial scale of the area of interest. In contrast, particle tracking results showed that incorporating a heterogeneous K field significantly enhanced the spatial distribution of particle trajectories indicative of reagent mixing. These findings support the hypothesis that the same well system used to invoke chaotic advection can be combined with SSHT analysis as a viable site characterization tool for delineating the spatial variability of K. Incorporating this K tomogram in a groundwater flow model with a particle tracking engine can be used as a design tool to aid in the selection of a site-specific RPM flow protocol to achieve enhanced reagent mixing.

Efficacy of a 14-day course of amoxicillin for patients with erythema migrans.

Although a 14-day treatment course with amoxicillin is in wide clinical usage to treat early Lyme disease, only a few published studies exist to validate its efficacy and safety, with none in the United States. In this study, we reviewed the records of 24 prospectively followed adult patients with erythema migrans who were prescribed a 14-day course of amoxicillin, 500 mg 3 times daily. Treatment with amoxicillin was well tolerated and uniformly successful in resolving the erythema migrans skin lesion and in preventing the development of an objective neurologic, cardiac, or rheumatologic manifestation. Although the study was relatively small and only involved a single center, the findings provide additional evidence that a 14-day course of 500 mg amoxicillin given 3 times per day is highly effective therapy for patients with early Lyme disease.