Tracer movements in a straight uniform flow: New equations for the advective part considering the distortion of flow lines around the well.

Methods for interpreting tracer tests often rely on equations assuming a natural regional flow which is straight and uniform. The main purpose of this project was to develop more realistic equations for the advective part of contaminant transport, by including the flow lines distortion occurring in the vicinity of the injection well. The complex potential of the flow during a tracer test was calculated by superimposing the complex potential of a natural, straight and uniform flow distorted by the presence of a passive well, and the complex potential of a radial flow corresponding to an isotropic injection alone. The equations were developed for a horizontal plan and the calculated complex potential yielded a groundwater velocity field, and after that a formula connecting the position of the advancing front of the tracer plume to the injection duration. These new equations were then tested with numerical simulations. A two-dimensional aquifer plan was modeled and set in order to numerically solve particle tracking and travel time computation of the moving front within a reasonable calculation time. This model provided a comparison of times needed to fully recover the tracer plume previously injected, the one calculated with the new equations and the one calculated with former equations neglecting the impact of the well presence on the groundwater flow field. The results showed that the new equations are significantly more precise, in particular when the injection rate is sufficiently low compared to the natural regional flow rate, with a relatively large well diameter and in the vicinity of the injection well. Three different plume shapes could be visualized numerically, and those shapes depend on the value of a parameter △ which compares the velocity component caused by the injection in the well and the component caused by the natural regional flow.

Persistence with osteoporosis treatment in patients from the Lille University Hospital Fracture Liaison Service.

PURPOSE/INTRODUCTION: A Fracture Liaison Service (FLS) was set up at Lille University Hospital in 2016. The purpose of this study was to assess persistence with osteoporosis treatment in patients from the FLS over a period of 1 year, and to determine predictors of discontinuation. METHODS: The study population comprised adults of both genders, aged 50 or over, admitted to Lille University Hospital between January 2016 and January 2019 for a low-trauma fracture and managed in our FLS. Outcomes included (1) persistence rate at 1 year after treatment initiation, (2) persistence rate at 2 years after treatment initiation, (3) persistence rate at 1 and 2 years after treatment initiation according to type of treatment, (4) predictors of non-persistence, and (5) reasons for discontinuing treatment over 1 year after initiation. Persistence was determined using the Kaplan-Meier method. RESULTS: In all, 1224 patients (≥50 years old) with a recent history of low-trauma fracture (≤12 months) were identified. Of these, 380 patients - 79.2% female; mean (SD) age 76 (11) years - were seen at the FLS. In those 380 patients, 410 fractures were found and 360 of them (87.8%) were major fractures, breaking down as follows: vertebra (44%), hip (19%), proximal humerus (10%), and pelvis (8%). Osteoporosis treatment was prescribed for 367 (96.6%) patients and 275 of them began the prescribed treatment. The following anti-osteoporosis drugs were prescribed: zoledronic acid (n=150, 54.5%), teriparatide (n=63, 22.9%), and denosumab (n=39, 14.2%). Oral bisphosphonates were prescribed for a few patients (n=23, 8.4%). Persistence with osteoporosis medication (any class) was estimated at 84.1% (95% CI: 79.1% to 88.1%) at 12-month follow-up, and dropped to 70.3% (95% CI: 63.7% to 75.9%) at 24 months. When drug-specific analyses were performed using the Kaplan-Meier method, persistence rates at 12 and 24 months were found to be higher with denosumab than with any other treatment. Independent predictors of non-persistence at 12 months were 'follow-up performed by a general practitioner (GP)' - Odds Ratio (OR) for GP vs. FLS = 3.68; 95% CI, 1.52 to 8.90, p=0.004 - and 'treatment with zoledronic acid' - OR for zoledronic acid vs. denosumab = 3.39; 95% CI, 1.21 to 9.50, p=0.019; OR for zoledronic acid vs. teriparatide = 8.86; 95% CI, 1.15 to 68.10, p=0.035. CONCLUSIONS: This study provides evidence of the success of our FLS in terms of long-term persistence with osteoporosis treatments. However, osteoporosis treatment initiation still needs to be improved.